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Salvia miltiorrhiza Bge (SMB) has long been used in traditional Chinese medicine to treat cardiovascular and cerebrovascular diseases. Growing clinical usage has led to a huge demand for artificial planting of SMB. Thus, continuous cropping of SMB is an important challenge that needs to be addressed. Continuous cropping can alter the metabolic profile of plants, resulting in poor growth and low yield. In this study, we attempted to image the spatial location and variation of endogenous metabolites in continuously cropped SMB using matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI). Spatially resolved expression of tanshinones, salvianolic acids, polyamines, phenolic acids, amino acids, and oligosaccharides in normal and continuously cropped SMB roots was compared. The expression of dihydrotanshinone I, tanshinone II A, dehydromiltirone, miltirone, dehydrotanshinone IIA, spermine, salvianolic acid B/E, tetrasaccharide, and pentasaccharide in continuously cropped SMB roots were much lower than that in normal roots. There was little difference in the expression of caffeic acid and salvianolic acid A in normal and continuously cropped SMB roots. Ferulic acid was more widely distributed in the xylem regions of normal SMB but strongly expressed in the xylem, phloem, and cambium of continuously cropped SMB. The spatially resolved metabolite information enhances our understanding of the metabolic signature of continuously cropped SMB and also provides insights into the metabolic effects of continuous cropping in other plants.

In rice (Oryza sativa L.), vascular bundle phloem tissue in the panicle neck is vital for the transport of photosynthetic products from leaf to panicle and is positively associated with grain yield. However, genetic regulation of the single large vascular bundle phloem area (LVPA) in rice panicle neck tissue remains poorly understood. In this study, we carried out genome-wide association analysis of LVPA in the panicle neck using 386 rice accessions and isolated and characterized the gene LVPA4, which is allelic to NARROW LEAF1 (NAL1). Phenotypic analyses were carried out on the near-isogenic line (NIL) NIL-LVPA4LT in the high-yielding indica (xian) cultivar Teqing and on overexpression lines transformed with a vector carrying the Lemont alleles of LVPA4. Both NIL-LVPA4LT and LVPA4 overexpression lines exhibited significantly increased LVPA, enlarged flag leaf size, and improved panicle type. NIL-LVPA4LT had a 7.6%–9.6% yield increase, mainly due to the significantly higher filled grain number per panicle, larger vascular system for transporting photoassimilates to spikelets, and more sufficient source supply that could service the increased sink capacity. Moreover, NIL-LVPA4LT had improved grain quality compared with Teqing, which was mainly attributed to substantial improvement in grain filling, especially for inferior spikelets in NIL-LVPA4LT. The single-nucleotide variation in the third exon of LVPA4 was associated with LVPA, spikelet number, and leaf size throughout sequencing analysis in 386 panels. The results demonstrate that LVPA4 has synergistic effects on source capacity, sink size, and flow transport and plays crucial roles in rice productivity and grain quality, thus revealing the value of LVPA4 in rice breeding programs for improved varieties.

The growing demand for food, combined with a strong social expectation for a diet produced with fewer conventional agrochemical inputs, has led to the development of new alternatives in plant protection worldwide. Among different possibilities, the stimulation of the plant innate immune system by chemicals represents a novel and promising way. The vectorization strategy of an active ingredient that we previously developed with fungicides can potentially extend to salicylic acid (SA) or its halogenated analogues.Using the click chemistry method, six new conjugates combining SA or two mono- or di-halogenated analogues with L-glutamic acid or β-D-glucose via a 1,2,3-triazole nucleus have been synthesized. Conjugate 8a, which is derived from SA and glutamic acid, showed high phloem mobility in the Ricinus model, similar to that of SA alone despite a much higher steric hindrance. In vivo bioassays of the six conjugates against two maize pathogenic fungi Bipolaris maydis and Fusarium graminearum revealed that, unlike SA, the amino acid conjugate 8a with good phloem mobility exerted a protective effect not only locally at the application site, but also in distant stem tissues after foliar application. Moreover, compounds 8a and 8b induced up-regulation of both defense-related genes ZmNPR1 and ZmPR1 similar to their parent compounds upon challenge inoculation with B. maydis.The vectorization of salicylic acid or its halogenated derivatives by coupling them with an α-amino acid can be a promising strategy to stimulate SA-mediated plant defenses responses against pathogens outside the application site. © 2022 The Authors. Pest Management Science published by John WileySons Ltd on behalf of Society of Chemical Industry.

Although the phloem is a highly specialized tissue, certain pathogens, including phytoplasmas, spiroplasmas, and viruses, have evolved to access and live in this sequestered and protected environment, causing substantial economic harm. In particular, Candidatus Liberibacter spp. are devastating citrus in many parts of the world. Given that most phloem pathogens are vectored, they are not exposed to applied chemicals and are therefore difficult to control. Furthermore, pathogens use the phloem network to escape mounted defenses. Our review summarizes the current knowledge of phloem anatomy, physiology, and biochemistry relevant to phloem/pathogen interactions. We focus on aspects of anatomy specific to pathogen movement, including sieve plate structure and phloem-specific proteins. Phloem sampling techniques are discussed. Finally, pathogens that cause particular harm to the phloem of crop species are considered in detail.

Phloem unloading plays an important role in photoassimilate partitioning and grain yield improvements in cereal crops. The phloem unloading strategy and its effects on photoassimilate translocation and yield formation remain unclear in rice. In this study, plasmodesmata were observed at the interface between the sieve elements (SEs) and companion cells (CCs), and between the SE–CC complex and surrounding parenchyma cells (PCs) in phloem of the dorsal vascular bundle in developing caryopses. Carboxyfluorescein (CF) signal was detected in the phloem of caryopses, which showed that CF was unloaded into caryopses. These results indicated that the SE–CC complex was symplasmically connected with adjacent PCs by plasmodesmata. Gene expression for sucrose transporter (SUT) and cell wall invertase (CWI), and OsSUT1 and OsCIN1 proteins were detected in developing caryopses, indicating that rice plants might actively unload sucrose into caryopses by the apoplasmic pathway. Among three rice recombinant inbred lines, R201 exhibited lower plasmodesmal densities at the boundaries between cell types (SE–CC, SE–PC and CC–PC) in developing caryopses than R91 and R156. R201 also had lower expression of SUT and CWI genes and lower protein levels of OsSUT1 and OsCIN1, as well as CWI activity, than R91 and R156. These data agreed with stem non-structural carbohydrate (NSC) translocation and grain yields for the three lines. The nitrogen application rate had no significant effect on plasmodesmal densities at the interfaces between different cells types, and did not affect CF unloading in the phloem of developing caryopses. Low nitrogen treatment enhanced expression levels of OsSUT and OsCIN genes in the three lines. These results suggested that nitrogen application had no substantial effect on symplasmic unloading but affected apoplasmic unloading. Therefore, we concluded that poor symplasmic and apoplasmic unloading in developing caryopses might result in low stem NSC translocation and poor grain yield formation of R201.

Incomplete knowledge of carbon (C) allocation dynamics in trees hinders accurate modeling and future predictions of tree growth. We studied C allocation dynamics in a mature Pinus sylvestris L. dominated forest with a novel analytical approach, allowing the first comparison of: (i) magnitude and delta C-13 of shoot, stem and soil CO2 fluxes (A(shoot), R-stem and R-soil), (ii) concentration and delta C-13 of compound-specific and/or bulk non-structural carbohydrates (NSCs) in phloem and roots and (iii) growth of stem and fine roots. Results showed a significant effect of phloem NSC concentrations on tracheid growth, and both variables significantly impacted R-stem. Also, concentrations of root NSCs, especially starch, had a significant effect on fine root growth, although no effect of root NSC concentrations or root growth was detected on R-soil. Time series analysis between delta C-13 of A(shoot) and delta C-13 of R-stem or delta C-13 of R-soil revealed strengthened C allocation to stem or roots under high C demands. Furthermore, we detected a significant correlation between delta C-13 of R-stem and delta C-13 of phloem sucrose and glucose, but not for starch or water-soluble carbohydrates. Our results indicate the need to include C allocation dynamics into tree growth models. We recommend using compound-specific concentration and delta C-13 analysis to reveal C allocation processes that may not be detected by the conventional approach that utilizes bulk organic matter.

Leaf cell sorting and scRNA-seq approaches are used to transcriptionally profile the palisade mesophyll layer and provide resources for understanding mesophyll biology. Like other complex multicellular organisms, plants are composed of different cell types with specialized shapes and functions. For example, most laminar leaves consist of multiple photosynthetic cell types. These cell types include the palisade mesophyll, which typically forms one or more cell layers on the adaxial side of the leaf. Despite their importance for photosynthesis, we know little about how palisade cells differ at the molecular level from other photosynthetic cell types. To this end, we have used a combination of cell-specific profiling using fluorescence-activated cell sorting and single-cell RNA-sequencing methods to generate a transcriptional blueprint of the palisade mesophyll in Arabidopsis thaliana leaves. We find that despite their unique morphology, palisade cells are otherwise transcriptionally similar to other photosynthetic cell types. Nevertheless, we show that some genes in the phenylpropanoid biosynthesis pathway have both palisade-enriched expression and are light-regulated. Phenylpropanoid gene activity in the palisade was required for production of the ultraviolet (UV)-B protectant sinapoylmalate, which may protect the palisade and/or other leaf cells against damaging UV light. These findings improve our understanding of how different photosynthetic cell types in the leaf can function uniquely to optimize leaf performance, despite their transcriptional similarities. NSF [DBI-0735191, DBI-1743442]; NIH-NCI CCSG [P30 014195, S10-OD023689]; Chapman Foundation; Helmsley Charitable Trust Published version We thank J. Mertens, C. Fitzpatrick, L Baum, M. Ku, N. Hah, and L. Ouyang for technical assistance. Some analysis was performed using CyVerse, supported by the NSF (DBI-0735191 and DBI-1743442), and the Flow Cytometry and NGS Core Facilities of the Salk Institute, with funding from NIH-NCI CCSG: P30 014195 and Shared Instrumentation Grant S10-OD023689; and NIH-NCI CCSG: P30 014195, the Chapman Foundation and the Helmsley Charitable Trust, respectively.

Stigmaria asiatica Jongmans et Gothan is a common species from the Permo-Carboniferous of East Asia. It is characterized by a relatively slender rhizomorph and represents the underground rooting system of lowland arborescent lycopsids. This species from the Wuda Coalfield (Asselian, lower Permian) represents the recovery taxon dominating the subsequent peat-forming vegetation after a volcanic eruption destroyed the previous flora, termed the Wuda Tuff Flora (Chinese “vegetational Pompeii”). It is characterized by novel downward axes, probably for access to deeper groundwater. Here, the anatomy of S. asiatica, including that of the axes and rootlets, is reported in detail for the first time. The axis contains stelar tissues, including pith, primary and secondary xylem, and phloem, and both primary and secondary cortical tissues. The primary cortex is tripartite and is divided into inner, middle, and outer zones. Secondary cortex is produced in the interior of the outer cortex splitting the outer cortex into inner and outer portions. The homogeneous pith and mesarch primary xylem maturation of S. asiatica are different from previously recorded species of Stigmaria Brongniart. Rootlets are composed of a central monarch vascular bundle surrounded by inner cortex and a ring of outer cortex. A vacant region is present between the inner and outer cortices. In some cases, connectives between the inner and outer cortices are present. According to the presented statistical analysis, it is proposed that rootlets of S. asiatica were highly branched, with at least for 7 bifurcations. Rootlets, together with the downward penetrating rhizomorph, helped to both anchor the plant and search for and absorb deep groundwater.

Changes in the substances in phloem sap can effectively reflect the nutritional status of cucumber plants during their growth. Because of the limitations of the time-consuming and complex operations of existing phloem sap extraction methods, the authors proposed a new extraction method based on the capillary-air pressure principle and designed a new sap sampling device. To examine the feasibility of the new sampling device, sap sampled from the same plant with the new method and the common EDTA method was analyzed by gas-phase mass spectrometry. The data showed that the number of substances in the sap sampled using capillary–air pressure was higher than that observed using the EDTA method. The concentration of substances sampled using capillary–air pressure was much higher than that observed using EDTA.

In Arabidopsis, polarized deposition of wall ingrowths in phloem parenchyma (PP) transfer cells (TCs) occurs adjacent to cells of the sieve element/companion cell (SE/CC) complex. However, the spatial relationships between these different cell types in minor veins, where phloem loading occurs, are poorly understood. PP TC development and wall ingrowth localization were compared with those of other phloem cells in leaves of Col-0 and the transgenic lines AtSUC2::AtSTP9-GFP (green fluorescent protein) and AtSWEET11::AtSWEET11-GFP that identify CCs and PP cells, respectively. The development of PP TCs in minor veins, indicated by deposition of wall ingrowths, proceeded basipetally in leaves. However, not all PP cells develop wall ingrowths, and higher levels of deposition occur in abaxial- compared with adaxial-positioned PP TCs. Furthermore, the deposition of wall ingrowths was exclusively initiated on and preferentially covered the PP TC/SE interface, rather than the PP TC/CC interface, and only occurred in PP cells that were adjacent to SEs. Collectively, these results demonstrate a tight association between SEs and wall ingrowth deposition in PP TCs and suggest the existence of two subtypes of PP cells in leaf minor veins. Compared with PP cells, PP TCs showed more abundant accumulation of AtSWEET11–GFP, indicating functional differences in phloem loading between PP and PP TCs.

There is now a wealth of data, from different plants and labs and spanning more than two decades, which unequivocally demonstrates that RNAs can be transported over long distances, from the cell where they are transcribed to distal cells in other tissues. Different types of RNA molecules are transported, including micro- and messenger RNAs. Whether these RNAs are selected for transport and, if so, how they are selected and transported remain, in general, open questions. This aspect is likely not independent of the biological function and relevance of the transported RNAs, which are in most cases still unclear. In this review, we summarize the experimental data supporting selectivity or nonselectivity of RNA translocation and review the evidence for biological functions. After discussing potential issues regarding the comparability between experiments, we propose criteria that need to be critically evaluated to identify important signaling RNAs.

The continuous growth of the global population and the increase in the amount of arid land has severely constrained agricultural crop production. To solve this problem, many researchers have attempted to increase productivity through the efficient distribution of energy; however, the direct relationship between the plant vasculature, specifically phloem development, and crop yield is not well established. Here, we demonstrate that an optimum increase in phloem-transportation capacity by reducing SIJUL expression leads to improved sink strength in tomato (Solanum lycopersicum L.). SIJUL, a negative regulator of phloem development, suppresses the translation of a positive regulator of phloem development, SlSMXL5. The suppression of SlJUL increases the number of phloem cells and sucrose transport, but only an optimal reduction of SlJUL function greatly enhances sink strength in tomato, improving fruit setting, and yield contents by 37% and 60%, respectively. We show that the increment in phloem cell number confers spare transport capacity. Our results suggest that the control of phloem-transport capacity within the threshold could enhance the commitment of photosynthates to instigate yield improvement.

In most plant tissues, threads of cytoplasm, or plasmodesmata, connect the protoplasts via pores in the cell walls. This enables symplasmic transport, for instance in phloem loading, transport and unloading. Importantly, the geometry of the wall pore limits the size of the particles that may be transported, and also (co-)defines plasmodesmal resistance to diffusion and convective flow. However, quantitative information on transport through plasmodesmata in non-cylindrical cell wall pores is scarce. We have found conical, funnel-shaped cell wall pores in the phloem-unloading zone in growing root tips of five eudicot and two monocot species, specifically between protophloem sieve elements and phloem pole pericycle cells. 3D reconstructions by electron tomography suggested that funnel plasmodesmata possess a desmotubule but lack tethers to fix it in a central position. Model calculations showed that both diffusive and hydraulic resistance decrease drastically in conical and trumpet-shaped cell wall pores compared with cylindrical channels, even at very small opening angles. Notably, the effect on hydraulic resistance was relatively larger. We conclude that funnel plasmodesmata generally are present in specific cell–cell interfaces in angiosperm roots, where they appear to facilitate symplasmic phloem unloading. Interestingly, cytosolic sleeves of most plasmodesmata reported in the literature do not resemble annuli of constant diameter but possess variously shaped widenings. Our evaluations suggest that widenings too small for unambiguous identification on electron micrographs may drastically reduce the hydraulic and diffusional resistance of these pores. Consequently, theoretical models assuming cylindrical symmetries will underestimate plasmodesmal conductivities.

Pollen fertility is critical for successful fertilization and, accordingly, for crop yield. While sugar unloading affects growth and development of all types of sink organs, the molecular nature for sugar import to tomato pollen is poorly understood. However, SWEET transporters have been proposed to function in pollen development. Here, qRT-PCR revealed that SlSWEET5b was markedly expressed in flowers when compared to the remaining tomato SlSWEETs; particularly, in the stamens of maturing flower buds undergoing mitosis. Distinct accumulation of SlSWEET5b-GUS fusion proteins was present in mature flower buds, especially in anther vascular and inner cells, symplasmic isolated pollen cells and styles. The demonstration that GFP fusion proteins located to the plasma membrane support the idea that the SlSWEET5b carrier functions in apoplasmic sugar translocation during pollen maturation. Such function is in line with data from yeast complementation experiments and radiotracer uptakes, showing that SlSWEET5b operates as a low affinity hexose-specific passive facilitator, with a KM of ~36 mM. Most importantly, RNAi-mediated suppression of SlSWEET5b expression resulted in shrunken nucleus-less pollen cells, impaired germination and low seed yield. Interestingly, stamens from SlSWEET5b-silenced tomato mutants contained significantly lower amounts of sucrose and increased invertase activity, pointing to reduced carbon supply and perturbed sucrose homeostasis in this tissue. Taken together, our findings reveal an essential role of SlSWEET5b in mediating apoplasmic hexose import into phloem unloading cells and into developing pollen cells to support pollen mitosis and maturation in tomato flowers.One-sentence SummaryPlasma-membrane-localized SlSWEET5b facilitates a sequential hexose flux, from phloem to anther cells and from anther locule to pollen, to support pollen maturation and fertility in tomato flowers.

Oryza sativa L. ssp. japonica cv. Nipponbare produces a nonproteinogenic amino acid (3R)-β-tyrosine from l-tyrosine by tyrosine aminomutase (OsTAM1). However, physiological and ecological function(s) of β-tyrosine have remained obscure. Often an improved understanding of metabolite localization and transport can aid in design of experiments to test physiological functions. In the current study, we investigated the distribution pattern of β-tyrosine in rice seedlings and found that β-tyrosine is most abundant in the youngest leaves. Based upon observations of high TAM1 activity in mature leaves, we hypothesized that β-tyrosine is transported from mature leaves to young leaves. Patterns of predominant mature synthesis and young leaf accumulation were supported by stable isotope studies using labeled β-tyrosine and the removal of mature leaves. Stem exudate analyses was also consistent with β-tyrosine transport through phloem. Thus, we identify young leaves as a key target in efforts to understand the biological function(s) of β-tyrosine in rice.

Aphids, the phloem sap feeders, probe into leaf tissues and activate a complex network of plant defense responses. Phytohormonal signaling plays a major role in this network; however, the dynamics of the signal spreading is yet to be clarified. Despite the growing knowledge about transcriptomic changes upon infestation, results often differ due to sampling, varying strongly between the tissues collected at the single feeding site, individual leaves, pooled infested leaves, or whole plant rosettes. This study focuses on activation of salicylic acid (SA) and jasmonic acid (JA) signals in Arabidopsis leaves during infestation by cabbage aphid (Brevicoryne brassicae) in high spatio-temporal resolution. We used genetically encoded fluorescent biosensors, histochemistry, and quantitative reverse transcription-PCR to precisely map activation of distinct branches of phytohormonal signaling. We found a rapid induction of SA and JA signaling markers in cells surrounding stylet puncture, colocalizing with callose deposition. For both PR1 and JAZ10, we detected activation at 24 h postinfestation (hpi), increasing and spreading along the veins until 72 hpi and, to a lesser extent, within the epidermal pavement cells. The SA signaling wave appeared in parallel with JA-associated signaling and continued to increase in time. Our results first show a local activation of SA- and JA-related responses after stylet penetration of Arabidopsis leaves and bring a detailed insight into the spatio-temporal complexity of plant defense activation during specialist aphid attack. [Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Phloem protein 2 (PP2) is a protein having lectin properties that can be isolated from the phloem sap. Based on our previous proteomic study of phloem sap of Cucumis sativus, it was found that the expression of PP2 A1-like was significantly up-regulated under salt stress, which may be a molecular mechanism of plant adaptation to stress. This paper carried out the expression and purification of the CsPP2-A1 gene in E. coli for further characteristic analysis. The results demonstrated that the CsPP2-A1 in shake flask cultures was mainly expressed in the soluble form at 15 °C or in inclusion bodies at 37 °C. Secondly, Ni-IDA affinity chromatography and SDS-PAGE were employed to yield highly purified CsPP2-A1 protein. The purified CsPP2-A1 was then subjected to Western blot and MALDI-TOF-MS analysis for protein identification. The biological activity analysis results showed that CsPP2-A1 had hemagglutinating activities to rabbit erythrocytes, and Chitotetraose may be the specific inhibitory sugar of CsPP2-A1. The optimal hemagglutination activity of CsPP2-A1 protein was achieved between pH 5–9, and between 20 and 60 °C. Moreover, CsPP2-A1 had significant inhibitory effects on Botrytis cinerea and Phytophthora infestans, and the inhibitory effect on B. cinerea was better than that on P. infestans.

BACKGROUND Tobacco sore shin caused by Rhizoctonia solani Kuhn is a major soil-borne fungal disease of tobacco, gradually causing infected stems to become thin and dry, leading to great losses to China's tobacco industry. Fungicides with phloem mobility are needed for application to foliage to effectively control root or vascular system pathogens. In this study, phenazine-1-carboxylic-valine (PCA-Val) conjugate with strong phloem mobility was tested for control of tobacco sore shin. In vitro fungicidal activity, systemicity, and in vivo efficacy of PCA-Val conjugate against R. solani in tobacco seedling were evaluated. RESULTS In vitro fungicidal activity of PCA-L-Val against R. solani was lower than that of PCA or PCA-D-Val, but the in vivo protective activity and curative activity of PCA-L-Val was the highest among these chemicals tested. The systemicity tests in tobacco seedlings revealed that PCA did not possess phloem mobility, while PCA-L-Val and PCA-D-Val exhibited strong phloem mobility and could be transported and accumulated in the lower part of the seedling as well as throughout the phloem. In addition, we also found that, just like reported hormone amino acid conjugates, PCA-L-Val could be hydrolyzed by tobacco seedlings, to release free PCA. CONCLUSIONS The current research results indicated that PCA-L-Val possess good phloem transport in tobacco and promising in vivo antifungal activity against R. solani, which can be used as a phloem-mobile fungicide against tobacco sore shin in production practice. This article is protected by copyright. All rights reserved.

Photosynthetic efficiency and sink demand are tightly correlated with rates of phloem loading where maintaining low cytosolic sugar concentrations is paramount to prevent downregulation of photosynthesis. Sugars Will Eventually be Exported Transporters (SWEETs) are thought to have a pivotal role in apoplastic phloem loading of C4 grasses. SWEETs have not been well-studied in C4 species, and their investigation is complicated by photosynthesis taking place across two cell types and therefore, photoassimilate export can occur out of either one. SWEET13 homologues in C4 grasses have been proposed to facilitate apoplastic phloem loading. Here we provide evidence for this hypothesis using the C4 grass Setaria viridis. Expression analyses on the leaf gradient of C4 species Setaria and sorghum show abundant transcript levels for SWEET13 homologues. Carbohydrate profiling along the Setaria leaf show total sugar content to be significantly higher in the mature leaf tip compared with the younger tissue at the base. We present the first known immunolocalization results for SvSWEET13a and SvSWEET13b using novel isoform-specific antisera. These results show localization to the bundle sheath and phloem parenchyma cells of both minor and major veins. We further present the first transport kinetics study of C4 monocot SWEETs by utilizing a Xenopus laevis oocyte heterologous expression system. We demonstrate that SvSWEET13a and SvSWEET13b are high-capacity transporters of glucose and sucrose with a higher apparent Vmax for sucrose than glucose, typical of clade III SWEETs. Collectively, these results provide evidence for an apoplastic phloem loading pathway in Setaria and possibly other C4 species.

The translocation of photosynthate carbohydrates, such as sucrose, is critical for plant growth and crop yield. Previous studies have revealed that sugar transporters, plasmodesmata and sieve plates act as important controllers in sucrose loading into and unloading from phloem in the vascular system. However, other pivotal steps for the regulation of sucrose movement remain largely elusive. In this study, characterization of two starch excesses in mesophyll (sem) mutants and dye and sucrose export assays were performed to provide insights into the regulatory networks that drive source-sink relations in rice. Map-based cloning identified two allelic mutations in a gene encoding a GLUCAN SYNTHASE-LIKE (GSL) protein, thus indicating a role for SEM1 in callose biosynthesis. Subcellular localization in rice showed that SEM1 localized to the plasma membrane. In situ expression analysis and GUS staining showed that SEM1 was mainly expressed in vascular phloem cells. Reduced sucrose transport was found in the sem1-1/1-2 mutant, which led to excessive starch accumulation in source leaves and inhibited photosynthesis. Paraffin section and transmission electron microscopy experiments revealed that less-developed vascular cells (VCs) in sem1-1/1-2 potentially disturbed sugar movement. Moreover, dye and sugar trafficking experiments revealed that aberrant VC development was the main reason for the pleiotropic phenotype of sem1-1/1-2. In total, efficient sucrose loading into the phloem benefits from an optional number of VCs with a large vacuole that could act as a buffer holding tank for sucrose passing from the vascular bundle sheath.

When perceiving microbe-associated molecular patterns (MAMPs) or plant-derived damage-associated molecular patterns (DAMPs), plants alter their root growth and development by displaying a reduction in the root length and the formation of root hairs and lateral roots. The exogenous application of a MAMP peptide, flg22, was shown to affect root growth by suppressing meristem activity. In addition to MAMPs, the DAMP peptide PEP1 suppresses root growth while also promoting root hair formation. However, the question of whether and how these elicitor peptides affect the development of the vascular system in the root has not been explored. The cellular receptors of PEP1, PEPR1 and PEPR2 are highly expressed in the root vascular system, while the receptors of flg22 (FLS2) and elf18 (EFR) are not. Consistent with the expression patterns of PEP1 receptors, we found that exogenously applied PEP1 has a strong impact on the division of stele cells, leading to a reduction of these cells. We also observed the alteration in the number and organization of cells that differentiate into xylem vessels. These PEP1-mediated developmental changes appear to be linked to the blockage of symplastic connections triggered by PEP1. PEP1 dramatically disrupts the symplastic movement of free green fluorescence protein (GFP) from phloem sieve elements to neighboring cells in the root meristem, leading to the deposition of a high level of callose between cells. Taken together, our first survey of PEP1-mediated vascular tissue development provides new insights into the PEP1 function as a regulator of cellular reprogramming in the Arabidopsis root vascular system.

Agarwood oil obtained from a number of genera of the family Thymelaeaceae is an expensive product in the global market. Gyrinops walla produces fragrant resinous substance similar to agarwood produced by Aquilaria spp. and Gonystylus spp. in mature and damaged stems and branches when they become infected with a particular type of mould. The present study focused on anatomical characteristics in healthy and infected wood of G. walla, and distribution of agarwood-type constituents based on their ecological habitats. Anatomical features of transverse, tangential and radial sections of healthy and infected wood samples were stained with safranin and observed under light microscope. The characteristics of wood colour, growth rings, vessel elements, ray parenchyma, axial parenchyma, intercellular spaces, tyloses and mineral inclusions and the distribution of phloem in wood sections were observed and described. White wood sections of G. walla were dried and grounded to execute solvent extraction. Thin-layer chromatography (TLC) and gas chromatography–mass spectroscopy (GC–MS) were performed to identify agarwood-type constituents in each geolocation. Wood anatomy of healthy and infected G. walla wood samples indicated similar anatomical features. Accumulated brownish substances in ray parenchyma, included phloem and xylem vessels in the wood signify the functional importance in agarwood production, and depositions in infected wood imply the involvement of living cells of the wood in the formation of agarwood and xylem as a storing tissue. Due to the appearance of higher amounts of sesquiterpenes on GC–MS analysis of wood extracts of samples collected from Gampaha District, Sri Lanka differs from the rest of the districts indicating an ecological provenance of agarwood formation in G. walla.

We wish to thank Elena Sanchez Romero (EEZ-CSIC) for her technical assistance, the Scientific Instrumentation Service at EEZ-CSIC, Granada, for their ICP-OES mineral analysis and Michael O'Shea for proofreading the manuscript. The study was funded by grant AGL201782452-C2-1R (A.B.) and grant AGL2017-82452-C2-2R (M.J.A.), both from the Spanish Ministerio de Ciencia e Innovacion/Agencia Estatal de Investigacion, MCIN/AEI/10.13039/501100011033, and FEDER "Una manera de hacer Europa", as well as grant ACCESP2018 (J.A.T.) from the University of Granada. J.E. was supported by a JAE Intro-CSIC grant, JAEINT_19_00566., We analyzed the physiological impact of function loss on cheesmaniae alleles at the HKT1;1 and HKT1;2 loci in the roots and aerial parts of tomato plants in order to determine the relative contributions of each locus in the different tissues to plant Na+/K+ homeostasis and subsequently to tomato salt tolerance. We generated different reciprocal rootstock/scion combinations with non-silenced, single RNAi-silenced lines for ScHKT1;1 and ScHKT1;2, as well as a silenced line at both loci from a near isogenic line (NIL14), homozygous for the Solanum cheesmaniae haplotype containing both HKT1 loci and subjected to salinity under natural greenhouse conditions. Our results show that salt treatment reduced vegetative growth and altered the Na+/K+ ratio in leaves and flowers; negatively affecting fruit production, particularly in graft combinations containing single silenced ScHKT1;2- and double silenced ScHKT1;1/ScHKT1;2 lines when used as scion. We concluded that the removal of Na+ from the xylem by ScHKT1;2 in the aerial part of the plant can have an even greater impact than that on Na+ homeostasis at the root level under saline conditions. Also, ScHKT1;1 function loss in rootstock greatly reduced the Na+/K+ ratio in leaf and flower tissues, minimized yield loss under salinity. Our results suggest that, in addition to xylem Na+ unloading, ScHKT1;2 could also be involved in Na+ uploading into the phloem, thus promoting Na+ recirculation from aerial parts to the roots. This recirculation of Na+ to the roots through the phloem could be further favoured by ScHKT1;1 silencing at these roots., Spanish Ministerio de Ciencia e Innovacion/Agencia Estatal de Investigacion AGL2017-82452-C2-1R AGL2017-82452-C2-2R, FEDER "Una manera de hacer Europa" MCIN/AEI/10.13039/501100011033, University of Granada ACCESP2018, JAE Intro-CSIC grant JAEINT_19_00566

There is an urgent need to stimulate agricultural output in many tropical and subtropical countries of the world to combat hunger and malnutrition. The starchy crop cassava (Manihot esculenta), growing even under sub-optimal conditions, is a key staple food in these regions, providing millions of people with food. Cassava biotechnology is an important technique benefiting agricultural progress, but successful implementation of many biotechnological concepts depends on the availability of the right spatiotemporal expression tools. Yet, well-characterized cassava promoters are scarce in the public domain. In this study, we investigate the promoter activity and tissue specificity of 24 different promoter elements in stably transformed cassava plants. We show that many of the investigated promoters, especially from other species, have surprisingly low activity and/or tissue specificity, but feature several promoter sequences that can drive tissue-specific expression in either autotrophic-, transport- or storage tissues. We especially highlight pAtCAB1, pMePsbR, and pSlRBCS2 as strong and specific source promoters, pAtSUC2, pMeSWEET1-like, and pMeSUS1 as valuable tools for phloem and phloem parenchyma expression, and pStB33, pMeGPT, pStGBSS1, as well as pStPatatin Class I, as strong and specific promoters for heterotrophic storage tissues. We hope that the provided information and sequences prove valuable to the cassava community by contributing to the successful implementation of biotechnological concepts aimed at the improvement of cassava nutritional value and productivity., Frontiers in Plant Science, 13, ISSN:1664-462X

Many woody plants produce large floral displays early in the spring when xylem transport can be variable and often reduced. To determine whether stem hydraulics impact floral water use, we quantified floral transpiration and tested whether it was correlated with stem xylem conductivity in five temperate woody species that flower before producing leaves. We measured inflorescence gas exchange, examined the relationship between diffusive conductance and inflorescence morphology, and estimated the amount of water supplied to an inflorescence by the phloem. We also tested for correlation between transpiration and native stem xylem conductivity for branches with leaves and branches with flowers. The flowers of our study species obtain most of their water from the xylem. Diffusive conductance was higher in small inflorescences, but water content and daily transpiration rates were greater for larger inflorescences. We found no correlation between floral transpiration per branch and stem xylem conductivity within species. The data suggest that inflorescence water loss during anthesis is not limited by the xylem in our study species. We highlight the impact of floral morphology on hydraulic traits and encourage exploration into temporal shifts in floral hydration.

The occurrence of water-soaked brown flesh in pear fruit is closely related to an activated biological Maillard reaction during the latter half of maturation. In this study, samples of immature and mature pear fruits were assessed for the incidence of water-soaked brown flesh (WSBF), sugar content, expression level of sugar metabolism-related genes, and activity of the Maillard and oxidative stress reactions. The occurrence of WSBF disorder was rare in immature fruit, but was pronounced in mature fruit. Glucose content of the flesh was higher in mature fruit with WSBF than in immature fruit without WSBF. Conversely, sucrose content was inversely correlated to glucose content. Higher levels of the neutral invertase gene (PpNIV) were detected in mature fruit compared with immature fruit. Levels of oxidative stress and Maillard reaction products in the flesh of mature fruit were determined. The strongest Maillard and oxidative stress reactions were observed in cells adjacent to the vascular bundle, and these reactions diminished with distance from the vascular bundle. Furthermore, examination of cells near the vascular bundle revealed stronger signal intensity on the phloem side compared to the xylem side. Cellular examination of the phloem side of immature and mature fruits indicated that mature fruit had a stronger signal intensity than immature fruit in both reactions. These results suggest that an increase in the Maillard reaction, attributed to an increased concentration of reducing sugars, during the maturation period may be fundamentally involved in the occurrence of this disorder through oxidative stress.

Whitefly (Bemisia tabaci) is a polyphagous insect that causes huge damage in several horticultural crops, including tomato, by sucking nutrients from the phloem and transmitting viruses. Whiteflies are particularly difficult to manage and the use of chemicals remains the common practice, which causes the development of insecticidal resistance. Thus, there is considerable interest in the introduction of resistance to whitefly by classical and molecular breeding. Here, we explored the concept of using an RNA interference construct to silence a v-ATPase gene in whiteflies interacting with transgenic tomato plants that express siRNA molecules corresponding to a fragment from the B. tabaci vATPase. PCR analyses revealed the presence of both ΔATPase and nptII transgenes in all transgenic lines. siRNA expressing lines were challenged against whitefly and revealed a mortality rate of 57.1% in transgenic line 4.4.1, while in the control the mortality was 7.6%. Mortality of 2nd instar nymphs was higher on the transgenic plants and the development of 3rd instar nymphs was slightly longer than on the control plants. Although the attraction of insects was not significantly different between treatments, the number of eggs laid by the insects on the transgenic plants was significantly lower, compared to the controls. RT-qPCR revealed a decreased expression level of endogenous v-ATPase gene in whiteflies feeding on transgenic plants. No unexpected effect was observed on the non-target insects Myzus persicae or Tuta absoluta. Results presented here may form the foundation for the generation of elite tomato varieties resistant to whitefly, a devastating insect pest. Genetically modified tomato was generated to express a vATPase small interfering RNA. Transgenic plants were tolerant to whiteflies (Bemisia tabaci) and revealed no effect on Myzus persicae and Tuta absoluta.

Symbiotic N2 fixation depends on a steady supply of carbohydrate to nodules. Sucrose is the main carbohydrate translocated through the phloem to nodules. Some putative sucrose transporter genes have been found in legumes and are highly expressed in nodules. However, none of these are crucial for sucrose transport to nodules. In this study, we characterized a soybean sucrose transporter, GmSUT1, which was highly expressed in nodules and mainly localized in peripheral fixation zone and vascular bundles of nodules. Soybean transgenic composite plants overexpressing GmSUT1 exhibited increased nodule number and dry weight, and improved plant dry weight and N content compared to control plants when inoculated with rhizobia. Furthermore, the inoculated RNAi plants impaired sucrose transport and showed increased shoot sucrose concentration. In nodules, overexpression of GmSUT1 decreased the sucrose concentration and increased hextose concentrations, whereas RNAi plants decreased glucose concentration compared with the control plants. These results in combination with the subcellular localization of GmSUT1 at the plasma membrane indicate that GmSUT1 plays a role in sucrose transport to nodules to promote soybean nodulation.

Phloem loading and transport are fundamental processes for allocating carbon from source organs to sink tissues. Cotton (Gossypium spp.) has a high sink demand for the cellulosic fibers that grow on the seed coat and for the storage reserves in the developing embryo, along with the demands of new growth in the shoots and roots. Addressing how cotton mobilizes resources from source leaves to sink organs provides insight into processes contributing to fiber and seed yield. Plasmodesmata frequencies between companion cells and flanking parenchyma in minor veins are higher than expected for an apoplastic loader, and cotton’s close relatedness to Tilia spp. hints at passive loading. Suc was the only canonical transport sugar in leaves and constituted 87% of 14C-labeled photoassimilate being actively transported. [14C]Suc uptake coupled with autoradiography indicated active [14C]Suc accumulation in minor veins, suggesting Suc loading from the apoplast; esculin, a fluorescent Suc analog, did not accumulate in minor veins. Of the nine sucrose transporter (SUT) genes identified per diploid genome, only GhSUT1-L2 showed appreciable expression in mature leaves, and silencing GhSUT1-L2 yielded phenotypes characteristic of blocked phloem transport. Furthermore, only GhSUT1-L2 cDNA stimulated esculin and [14C]Suc uptake into yeast, and only the GhSUT1-L2 promoter caused uidA (β-glucuronidase) reporter gene expression in minor vein phloem of Arabidopsis thaliana. Collectively, these results argue that apoplastic phloem loading mediated by GhSUT1-L2 is the dominant mode of phloem loading in cotton.

How carbohydrate reserves change in conifers during drought and bark beetle attacks are poorly understood. We investigated changes in carbohydrate reserves and carbon-dependent terpene defenses in ponderosa pine trees experimentally subjected to two levels of drought stress (via root trenching) and two types of biotic challenge treatments (pheromone-induced bark beetle attacks or inoculations with crushed beetles that include beetle-associated fungi) for two consecutive years. Our results showed that trenching did not influence carbohydrates whereas both biotic challenges reduced amounts of starch and sugars of trees. However, only the trenched-beetle attacked trees depleted carbohydrates and died within the first year of bark beetle attacks. While live trees contained higher carbohydrates than dying trees, amounts of constitutive and induced terpenes produced did not vary between live and beetle-attacked dying trees, respectively. Based on these results we propose that reallocation of carbohydrates to terpenes during the early stages of beetle attacks is limited in drought-stricken trees, and that the combination of biotic and abiotic stress leads to tree death. The process tree death is subsequently aggravated by beetle girdling of phloem, occlusion of vascular tissue by bark beetle-vectored fungi, and potential exploitation of host carbohydrates by beetle symbionts as nutrients.

The development of secondary vascular tissue enhances the transport capacity and mechanical strength of plant bodies, while contributing a huge proportion of the world’s biomass in the form of wood. Cell divisions in the cambium, which constitutes the vascular meristem, provide progenitors from which conductive xylem and phloem are derived. The cambium is a somewhat unusual stem cell population in two respects, making it an interesting subject for developmental research. Firstly, it arises post-germination, and thus represents a model for understanding stem cell initiation beyond embryogenesis. Secondly, xylem and phloem differentiate on opposing sides of cambial stem cells, making them bifacial in nature. Recent discoveries in Arabidopsis thaliana have provided insight into the molecular mechanisms that regulate the initiation, patterning, and maintenance of the cambium. In this review, the roles of intercellular signalling via mobile transcription factors, peptide–receptor modules, and phytohormones are described. Crosstalk between these regulatory pathways is becoming increasingly apparent, yet the underlying mechanisms are not fully understood. Future study of the interaction between multiple independently identified regulators, as well as the functions of their orthologues in trees, will deepen our understanding of radial growth in plants., We review the literature describing the molecular mechanisms by which the vascular cambium is initiated and maintained in Arabidopsis.

Vascular system plays an important role in plant growth and survival under dynamic environmental conditions. As part of vascular tissues, the phloem consists of phloem sieve elements (SEs) and companion cells (CCs). In the root apical meristem of Arabidopsis thaliana, CCs are generated by the asymmetric cell divisions (ACDs) of procambial cells adjoining SEs and pericycle cells. The proto- and metaphloem SEs are originated from sequential ACDs of a SE-procambium precursor and a SE precursor. To study the development of vascular tissues, researchers have mainly relied on histological methods that take days with multiple steps. While investigating molecular mechanisms underlying phloem SE development, we developed a rapid and reliable method that allows for the detection of differentiating phloem SEs. This protocol employs monoclonal anti-phloem sieve element (RS6) antibody, which was selected from hybridomas raised against SEs isolated from tissue cultures of California shield leaf, Streptanthus tortuosus. RS6 is known to recognize a SE-specific early nodulin-like protein, SE-ENOD, which is specifically localized to the plasma membrane of differentiating and mature SEs. This protocol enables quantitative assessment of phloem SEs on a large scale for a broad range of species beyond A. thaliana.

AKT2 potassium (K+) channels are members of the plant Shaker family which mediate dual-directional K+ transport with weak voltage-dependency. Here we show that OsAKT2 of rice (Oryza sativa) functions mainly as an inward rectifier with strong voltage-dependency and acutely suppressed outward activity. This is attributed to the presence of a unique K191 residue in the S4 domain. The typical bi-directional leak-like property was restored by a single K191R mutation, indicating that this functional distinction is an intrinsic characteristic of OsAKT2. Furthermore, the opposite R195K mutation of AtAKT2 changed the channel to an inward-rectifier similar to OsAKT2. OsAKT2 was modulated by OsCBL1/OsCIPK23, evoking the outward activity and diminishing the inward current. The physiological relevance in relation to the rectification diversity of OsAKT2 was addressed by functional assembly in the Arabidopsis (Arabidopsis thaliana) akt2 mutant. Overexpression (OE) of OsAKT2 complemented the K+ deficiency in the phloem sap and leaves of the mutant plants but did not significantly contribute to the transport of sugars. However, the expression of OsAKT2-K191R overcame both the shortage of phloem K+ and sucrose of the akt2 mutant, which was comparable to the effects of the OE of AtAKT2, while the expression of the inward mutation AtAKT2-R195K resembled the effects of OsAKT2. Additionally, OE of OsAKT2 ameliorated the salt tolerance of Arabidopsis., The presence of a unique K191 residue retains the activity of rice potassium channel OsAKT2 mainly as an inward rectifier (Mode I) that emphasizes its in planta role of phloem K+ translocation.

We have previously demonstrated that Arabidopsis (Arabidopsis thaliana) phloem protein PP2-A1 is an integral component of resistance to the green peach aphid (Myzus persicae). Here, we report that M. persicae overcomes the resistance of PP2-A1 by using the salivary protein Mp1 as an energetic effector and an interactor of AtPP2-A1. Using the RNA interference technique, we demonstrated that Mp1 plays an essential role in the phloem-feeding activity of M. persicae. When the Mp1 gene was silenced, aphids incurred serious impairments not only in phloem-feeding activity, but also in survival and fertility. In essence, phloem-feeding activity was attributed to the molecular interaction between Mp1 and AtPP2-A1. The Mp1 and AtPP2-A1 interactions were localized to plant cell membranes by co-immunoprecipitation and bimolecular fluorescence complementation experiments. Furthermore, the interaction was found to be required for aphid feeding on Arabidopsis phloem. Overall, our results suggest that Mp1 is an important effector of M. persicae and interacts with AtPP2-A1 to facilitate infestation in the plant tissue by this insect.

Phloem-feeding insects cause massive losses in agriculture and horticulture. Host plant resistance to phloem-feeding insects is often mediated by changes in phloem composition, which deter insect settling and feeding and decrease viability. Here, we report that rice plant resistance to the phloem-feeding brown planthopper (BPH) is associated with fortification of the sclerenchyma tissue, which is located just beneath the epidermis and a cell layer or two away from the vascular bundle in the rice leaf sheath. We found that BPHs prefer to feed on the smooth and soft region on the surface of rice leaf sheaths called the long-cell block. We identified Bph30 as a rice BPH resistance gene that prevents BPH stylets from reaching the phloem due to the fortified sclerenchyma. Bph30 is strongly expressed in sclerenchyma cells and enhances cellulose and hemicellulose synthesis, making the cell walls stiffer and sclerenchyma thicker. The structurally fortified sclerenchyma is a formidable barrier preventing BPH stylets from penetrating the leaf sheath tissues and arriving at the phloem to feed. Bph30 belongs to a novel gene family, encoding a protein with two leucine-rich domains. Another member of the family, Bph40, also conferred resistance to BPH. Collectively, the fortified sclerenchyma-mediated resistance mechanism revealed in this study expands our understanding of plant-insect interactions and opens a new path for controlling planthoppers in rice.

Bud endodormancy is accompanied by transport channel apertures blockage through callose deposition, and its resume to growth requires evoking β-1,3-glucanases (BGs) to unchoke the conduit. To understand out its working manner, the statuses of the transport channels were evaluated and candidate BGs were identified during chilling and gibberellin acids (GA) induced dormancy release in tree peony. Calcein reflects plasmodesmata permeability, and no calcein was observed in the bud together with density aniline blue fluorescent around the stem phloem at 0 d chilling. With the increase of chilling accumulation, the contents of glucan declined and the activities of gulcanase increased gradually in buds, and the calcein reached the top of flower primordia at 21 d chilled bud. Both GA3 and GA4 feedings promoted bud sprouting and growth along with rapidly unchoking the transport channels, and GA3 was more effective. Several candidate β-1,3-glucanase genes were detected, combining transcriptional profiling and quantitative PCR analysis. PsBG1, PsBG3, PsBG6, PsBG8 and PsBG9 were inducible by chilling accumulation and presented laminarin hydrolyzing activities after prokaryotically expression, while PsBG1, PsBG3, PsBG8 and PsBG9 responded to GAs application. Subcellular localizations revealed that PsBG6 and PsBG9 were plasmodesmata residents. It was concluded that PsBG6 played a vital role in chilling accumulation response and PsBG9 was central in GAs-induced dormancy release, and they could be used as marker genes for dormancy release in tree peony. These results were of great value to understand the mechanism of dormancy regulation and as an important fundamental for forcing culture technology in tree peony.

Aims: To evaluate pharmacognostic and preliminary phytochemical analysis of stem of Conocarpus lancifolius including macroscopic, microscopic and physicochemical parameters. Methods and Material: Macroscopic and microscopic properties of dried stem were investigated. Preliminary phytochemical analysis of various extracts and fluorescence analysis of dried stem powder was performed using various chemicals. Physicochemical parameters were evaluated as per WHO guidelines. Results: Organoleptic parameters of stem of C. lancifolius like colour, shape, size etc were noted. Transverse section of fresh stem revealed the presence of epidermis, cortex, sone cells, phloem, xylem and pith. Whereas, powder microscopy showed the presence of epidermis, xylem, stone cells, phloem fibre with crystals of calcium oxalate etc. Phytochemical screening of methanolic extract of stem showed presence of alkaloids, flavonoids, glycoside, steroids etc. Ethyl acetate extract showed the presence of alkaloids and steroids while aqueous extract showed presence of tannins. Physicochemical parameters viz. ash value, extractive value, moisture content, fluorescence analysis and foaming index of stem powder were determined. The total tannins were also determined in the stem of C. lancifolius. Conclusion: The present study revealed pharmacognostic and preliminary phytochemical parameters of stem of C. lancifolius which would be beneficial for its standardization and future scope of the work.

Made available in DSpace on 2022-04-29T08:34:54Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 The bark (all tissues outside the cambium) is a morphologically diverse and functionally important part of the stem. Outer bark (periderm) has a protective function, and inner bark (secondary phloem) is involved in the long-distance transport. In savannas, the relationship between bark structure, life form and habitat is controversial. We studied the morphology and anatomy of bark of Melastomataceae species with different habits growing at different sites in the Brazilian Cerrado (a neotropical savanna), from well-drained to temporarily or permanently waterlogged soils. Bark samples were processed by standard anatomical techniques. Regarding the outer bark, the species studied are grouped into two main categories: with a single periderm (with nonstratified or stratified phelem) and with multiple periderms, that is, with a rhytidome. Although a formal test has not been carried out in this work to assess the existence of a correlation between the microscopic structure of the periderm and the habit and growth distribution of plants, there seems to be no correlation for most of the species studied here, except for a subshrub species inhabiting waterlogged soils. Sclerified cells, calcium oxalate crystals, and phenolic content are abundant through the secondary phloem. Microscopic bark features are useful to distinguish species. 2021 Departamento de Ciências Biológicas UFES - Universidade Federal Do Espírito Santo Faculdade de Ciências Agronômicas Departamento de Ciência Florestal Solos e Ambiente UNESP - Universidade Estadual Paulista, CP 237 Departamento de Botânica UNESP - Univ Estadual Paulista Instituto de Biociências, CP 510 Faculdade de Ciências Agronômicas Departamento de Ciência Florestal Solos e Ambiente UNESP - Universidade Estadual Paulista, CP 237 Departamento de Botânica UNESP - Univ Estadual Paulista Instituto de Biociências, CP 510

Studies on the frost resistance of sweet cherries were carried out in 2019–2020 in the FSBSI of the Federal Horticultural Research Center for Breeding, Agrotechnology and Nursery in laboratory conditions by artificial freezing in the climate chamber TH-6 JEIO TECH-1000. Objects of research: Tyutchevka and Chermashnaya varieties grafted on 8 clonal rootstocks (Colt, Izmailovsky, AVCH-2, V-5-88, VC-13, Moskoviya, VSL-2, Stepnoy Rodnik). The aim of the research is to study the effect of clonal rootstocks on the frost resistance of cherry buds and tissues during the thaw and to identify the most frost-resistant scion-rootstock combinations for the 3rd component. It was found that after freezing at t = -20 °C during the thaw, the safety of flower buds in the Tyutchevka variety in both years of research was more than 80 %, and in the Chermashnaya variety — from 20 to 30 %, depending on the year. The limits of changes in the frost resistance of generative buds of varieties depending on the rootstock are shown: in the Tyutchevka variety — from 66.8 % (V-5-88) to 96.4 % (Izmailovsky), and in the Chermashnaya variety — from 7.7 % (V-5-88) to 65.5 % (AVCH-2). When using the AVCH-2 and Izmailovsky clonal rootstocks, the safety of flower buds increased by 30 % compared to the Colt rootstock. The most frost-resistant scion –rootstock combinations for each variety were identified: Tyutchevka/Izmailovsky and Tyutchevka/Stepnoy Rodnik, which preserved more than 90 % of the living rudiments; Chermashnaya/AVCH-2 (65.5 %) and Chermashnaya/Izmailovsky (40.1 %). Vegetative buds and tissues of annual branches were practically free of freezing in the studied varieties when grafted on the rootstocks of Stepnoy Rodnik and AVCH-2. In the Chermashnaya variety, damage of about 1 point of the phloem and vascular bundle under the buds was noted when grafting on rootstocks V-5-88 and Colt.

GIGANTEA (GI) genes have a central role in plant development and influence several processes. Hybrid aspen T89 (Populus tremula x tremuloides) trees with low GI expression engineered through RNAi show severely compromised growth. To study the effect of reduced GI expression on leaf traits with special emphasis on leaf senescence, we grafted GI-RNAi scions onto wild-type rootstocks and successfully restored growth of the scions. The RNAi line had a distorted leaf shape and reduced photosynthesis, probably caused by modulation of phloem or stomatal function, increased starch accumulation, a higher carbon-to-nitrogen ratio, and reduced capacity to withstand moderate light stress. GI-RNAi also induced senescence under long day (LD) and moderate light conditions. Furthermore, the GI-RNAi lines were affected in their capacity to respond to “autumn environmental cues” inducing senescence, a type of leaf senescence that has physiological and biochemical characteristics that differ from those of senescence induced directly by stress under LD conditions. Overexpression of GI delayed senescence under simulated autumn conditions. The two different effects on leaf senescence under LD or simulated autumn conditions were not affected by the expression of FLOWERING LOCUS T. GI expression regulated leaf senescence locally—the phenotype followed the genotype of the branch, independent of its position on the tree—and trees with modified gene expression were affected in a similar way when grown in the field as under controlled conditions. Taken together, GI plays a central role in sensing environmental changes during autumn and determining the appropriate timing for leaf senescence in Populus., In the autumn deciduous trees respond to environmental signals and induce leaf senescence, and two different senescence pathways can be distinguished

Plants constitute 80% of the biomass on earth, and almost two-thirds of this biomass is found in wood. Wood formation is a carbon (C)-demanding process and relies on C transport from photosynthetic tissues. Thus, understanding the transport process is of major interest for understanding terrestrial biomass formation. Here, we review the molecules and mechanisms used to transport and allocate C in trees. Sucrose is the major form in which C is transported in plants, and it is found in the phloem sap of all tree species investigated so far. However, in several tree species, sucrose is accompanied by other molecules, notably polyols and the raffinose family of oligosaccharides. We describe the molecules that constitute each of these transport groups, and their distribution across different tree species. Furthermore, we detail the metabolic reactions for their synthesis, the mechanisms by which trees load and unload these compounds in and out of the vascular system, and how they are radially transported in the trunk and finally catabolized during wood formation. We also address a particular C recirculation process between phloem and xylem that occurs in trees during the annual cycle of growth and dormancy. A search of possible evolutionary drivers behind the diversity of C-carrying molecules in trees reveals no consistent differences in C transport mechanisms between angiosperm and gymnosperm trees. Furthermore, the distribution of C forms across species suggests that climate-related environmental factors will not explain the diversity of C transport forms. However, the consideration of C-transport mechanisms in relation to tree–rhizosphere coevolution deserves further attention. To conclude the review, we identify possible future lines of research in this field.

Arbuscular mycorrhizal fungi (AMF) develop strong mutualistic associations with roots of about 70% of all vascular plants. By modifying host plant nutrient uptake, growth and defense, AMF also indirectly influence the aboveground herbivorous insect community. Since plant response to AMF depends on the extent of mycorrhization, outcomes of the bottom-up effects of AMF on herbivores are extremely variable and not well understood. We thus tested whether the generalist phloem feeder Bemisia tabaci (tobacco whitefly) was affected by the colonization of habanero pepper seedlings (Capsicum chinense) by different densities of the AMF Rhizophagus irregularis. After AMF inoculation (with control, low and high doses of liquid inoculum), seedlings were grown in a greenhouse without (control) and with whiteflies (10 adults per seedling). We measured plant traits and growth and biomass allocations at 2, 16 and 30 days after transplantation of emerged seedlings. We estimated whitefly adult, egg and nymph densities 28 days after transplantation. B. tabaci abundance significantly increased after C. chinense inoculation with low AMF density (120% increase for adults, 97% for eggs) through an augmentation of seedling nutritional status. By enhancing plant tolerance and primary metabolism, the higher density of AMF did not affect B. tabaci fitness on seedlings. We highlight here that whitefly abundance on mycorrhizal C. chinense varies widely depending on AMF inoculum concentration.

Valsa canker is a destructive fungal disease that results in a serious loss of production. The pathogen Valsa pyri (Vp) usually infiltrates the bark and xylem via the wound. ‘Duli’ (Pyrus betulifolia), a rootstock with high tolerance to this disease and multiple other stresses, is widely planted in northern China. We found that wound healing plays a crucial role in the resistance of ‘Duli’ against Vp infection. Nevertheless, elucidation of the molecular mechanism of this process has been largely limited. Using RNA sequencing (RNA-seq), we investigated dynamic gene expression profiles of ‘Duli’ and ‘Zaosu’ (Pyrus bretschneideri, susceptible) phloem tissues which 0–3 mm around the wounded site that were cultured for 1, 3, and 7 days after wounding. Quantitative real-time PCR (qRT-PCR) was used to confirm data veracity. After wounding at 1, 3, and 7 days, 4930, 4652, and 6279 differentially expressed genes (DEGs) were found from ‘Duli’, compared to 1641, 1968, and 3347 in ‘Zaosu’, respectively. Functional enrichment analysis revealed that the DEGs associated with “cell wall organization and biogenesis”, “biosynthesis of secondary metabolites” and “cell wall organization. pectin” were enriched both in ‘Duli’ and ‘Zaosu’. Additionally, expressions of DEGs encoding receptor-like kinase (RLK) subfamily Extensin, LRR-III, LRR-IV, LRR-IX, LRR-XI-1, LRR-XII-1, RLCK-IXa and RLCK-V, and transcription factor CRE1, TF, ABF, TGA, and MYC2 were rapidly activated in ‘Duli’, but only a subtle induction in ‘Zaosu’. In conclusion, DEGs related to cell wall thickening are rapidly and continuously induced in ‘Duli’, which plays a positive role in the formation of protective tissues. Notably, JA-, SA-, LRR-, RLCK-, and Extensin-related DEGs probably participated in the regulation of multiple molecular networks and contributed to the quick wound healing of ‘Duli’.

We studied the time-course of stem response for six months following complete girdling in branches of Aquilaria sinensis to determine the potential role of interxylary phloem (IP) in this response. It was found that the vascular cambium, as well as its derivative secondary xylem and phloem, regenerated fully through redifferentiation of IP. We confirmed that vascular cambium regenerated within one month after girdling based on observation of new vessels, IP, and secondary phloem fibers. The time-course study showed that IPs made connections with each other, merged, and became larger through the proliferation of IPs parenchyma cells and the cleaving of secondary xylem in a narrow zone 400 to 1000 μm deep inside the girdled edge. This led to the formation of a complete circular sheath of vascular cambium, followed by the regeneration of vascular tissue. It is worth noting that the secondary xylem is regenerated always following the formation of a thick belt of wound xylem.

To identify microorganisms that can colonise pine trees and have a toxic effect on Monochamus alternatus (Coleoptera: Cerambycidae), we isolated the CSHH2 bacterial strain from the phloem of nemato...

Phloem fibers from the bark of Pteroceltis tatarinowii are the main raw material for Chinese traditional handmade paper, Xuan zhi. Research on this fiber will contribute to unveil the scientific connotation contained in empirical records, and promote the inheritance of Chinese culture. In this study, the influence of age (5-, 12-, 29- year-old) on the anatomical, morphological, cellulose, and mechanical characteristics of phloem fibers were investigated. The microscopy showed that phloem fibers of P. tatarinowii contained the gelatinous layer. The phloem fibers were thin and long, and microfibril angles were small (4.2° ~ 6.9°). The highest total carbohydrate content of 38.0% was found in the 5-year-old bark, of which glucose accounted for 73.3%. The crystallinity of phloem fiber was decreased from 70.7 to 57.5 with the growing age. Due to a tighter cellulose structure, the 5-year-old phloem fibers exhibited a higher indentation modulus (10.8 ~20.5 GPa) than the others (6.1~15.0 GPa).

This research was conducted to investigate the effect of garlic cloves extract (GCE) at 50 and 100 g l-1 and licorice root extract (LRE) at 25 and 50 g l-1 as foliar spray treatments on the vegetative growth and leaf anatomy of strawberry plants cultivated in different growing media, i.e. traditional soil (silt : sand 1:1 v/v), solid substrates (Peatmoss, Perlite and vermiculite 1:1:1 v/v/v), hydroponic (DFT technique) during 2017 and 2018 seasons. The growth of strawberry plants cv. festival cultivated in the three assigned growing media was significantly enhanced by the applied GCE and LRE treatments. Significant increases in the fresh and dry weights of root and shoots, root size, number of leaves and total leaves area / plant were obtained with all GCE and LRE treatments, while a significant reduction in roots / shoots ratio was occurred. In addition, both treatments caused a significant increase in the leaf content of photosynthetic pigments, nitrogen, phosphorous, potassium, calcium, magnesium and crude protein compared with the untreated plants. Anatomically, the applied concentrations of both GCE and LRE led to obvious increases in the thickness of mid vein, length and width of main vascular bundle, thickness of phloem and xylem tissues, number of xylem vessels/ bundle and thickness of lamina and its tissue components (upper and lower epidermis and mesophyll tissue). Furthermore, these positive effects of GCE and LRE treatments on the vegetative growth, chemical composition and leaf anatomy were most pronounced with the plants cultivated in solid substrate mixture followed by the plants cultivated hydroponically then those cultivated in traditional soil. Also, LRE at 50 g l-1 was the most effective treatment in this respect followed by LRE at 25 g l-1 then GCE at 50 g l-1 while GCE at 100 g l-1 was the least effective. Therefore, the present study strongly confirm the use of GCE and LRE as healthy safe and eco-friendly treatments to improve growth of strawberry plants whether cultivated in traditional soil or in soil alternatives and also to reduce the risks of using growth regulators for clean and safe agriculture.

Premise of research. The alternative patterns of secondary growth (vascular cambial variants) in stems of Nyctaginaceae are outstanding and have been widely investigated since the late nineteenth c...

Huanglongbing (HLB) is currently considered the most destructive disease of citrus worldwide. In the major citrus-growing areas in Asia and the US, the major causal agent of HLB is the bacterial pathogen Candidatus Liberibacter asiaticus (CLas). CLas is vectored by the Asian citrus psyllid, Diaphorina citri, in a persistent propagative manner. CLas cannot be cultured in vitro because of its unclear growth factors, leading to uncertainty in the infection mechanism of CLas at the cellular level in citrus and in D. citri. To characterize the detailed infection of CLas in the host and vector, the incidence of HLB was first investigated in citrus-growing fields in Fujian Province, China. It was found that the positive association of the level of CLas infection in the leaves correlated with the symptoms. Then antibodies against peptides of the outer membrane protein (OMP) of CLas were prepared and tested. The antibodies OMP-225, OMP-333 and OMP724 showed specificity to citrus plants in western blot analyses, whereas the antibodies OMP-47 and OMP-225 displayed specificity to the D. citri vector. The application of OMP-225 in the immunofluorescence assay indicated that CLas was located in and distributed throughout the phloem sieve cells of the leaf midribs and axile placenta of the fruit. CLas also infected the epithelial cells and visceral muscles of the alimentary canal of D. citri. The application of OMP-333 in immunoelectron microscopy indicated the round or oval CLas in the sieve cells of leaf midribs and axile placenta of fruit as well as in the epithelial cells and reticular tissue of D. citri alimentary canal. These results provide a reliable means for HLB detection, and enlighten a strategy via neutralizing OMP to control HLB. These findings also provide insight for the further investigation on CLas infection and pathogenesis, as well as CLas-vector interaction.