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Desert-inhabiting cyanobacteria can tolerate extreme desiccation and quickly revive after rehydration. The regulatory mechanisms that enable their vegetative cells to resurrect upon rehydration are poorly understood. In this study, we identified a single gene family of high light-inducible proteins (Hlips) with dramatic expansion in the

Background Selenium (Se) deficiency caused a series of health disorders in human beings, and Se concentration in the edible parts of crops can be improved by altering exogenous Se species. However, the uptake, transport, subcellular distribution and metabolism of selenite, selenate and SeMet influenced by phosphorus (P) has not been well characterized. Results The resulted showed that increasing P supply enhanced photosynthesis and then increase the dry matter weight of shoots at selenite and SeMet, and appropriate P combined with selenite increased the dry matter weight of roots by enhancing root growth. At selenite, increasing P supply significantly decreased the concentration and accumulation of Se in roots and shoots. P1 decreased the Se migration coefficient, which could be attributed to the inhibited distribution of Se in root cell wall but increased distribution of Se in root soluble fraction, as well as the promoted proportion of SeMet and MeSeCys in roots. At selenate, P0.1 and P1 significantly increased the Se concentration and distribution in shoots and Se migration coefficient, which could be attributed to the enhanced proportion of Se(IV) in roots but decreased proportion of SeMet in roots. At SeMet, increasing P supply significantly decreased Se concentration in shoots and roots, but increased the proportion of SeCys in roots. Conclusion Compared with selenite or SeMet, appropriate P combined with selenite could promote plant growth, reduce Se uptake, alter Se subcellular distribution and speciation, and then affect the Se bioavailability in wheat.

Desert-inhabiting cyanobacteria can tolerate extreme desiccation and quickly revive after rehydration. The regulatory mechanisms that enable their vegetative cells to resurrect upon rehydration are poorly understood. In this study, we identified a single gene family of high light-inducible proteins (Hlips) with dramatic expansion in the Nostoc flagelliforme genome and found an intriguingly special convergence formed through four tandem gene duplication. The emerged four independent hlip genes form a gene cluster ( hlips-cluster ) and respond to dehydration positively. The gene mutants in N. flagelliforme were successfully generated by using gene-editing technology. Phenotypic analysis showed that the desiccation tolerance of hlips-cluster –deleted mutant decreased significantly due to impaired photosystem II repair, whereas heterologous expression of hlips-cluster from N. flagelliforme enhanced desiccation tolerance in Nostoc sp. PCC 7120. Furthermore, a transcription factor Hrf1 ( hlips-cluster repressor factor 1) was identified and shown to coordinately regulate the expression of hlips-cluster and desiccation-induced psbAs . Hrf1 acts as a negative regulator for the adaptation of N. flagelliforme to the harsh desert environment. Phylogenetic analysis revealed that most species in the Nostoc genus possess both tandemly repeated Hlips and Hrf1. Our results suggest convergent evolution of desiccation tolerance through the coevolution of tandem Hlips duplication and Hrf1 in subaerial Nostoc species, providing insights into the mechanism of desiccation tolerance in photosynthetic organisms.

The phytohormone abscisic acid (ABA) is crucial for plant responses to environmental challenges. The SNF1-regulated protein kinase 2s (SnRK2s) are key components in ABA-receptor coupled core signaling, and are rapidly phosphorylated and activated by ABA. Recent studies have suggested that Raf-like protein kinases (RAFs) participate in ABA-triggered SnRK2 activation. In vitro kinase assays also suggest the existence of autophosphorylation of SnRK2s. Thus, how SnRK2 kinases are quickly activated during ABA signaling still needs to be clarified. Here, we show that both B2 and B3 RAFs directly phosphorylate SnRK2.6 in the kinase activation loop. This transphosphorylation by RAFs is essential for SnRK2 activation. The activated SnRK2s then intermolecularly trans-phosphorylate other SnRK2s that are not yet activated to amplify the response. High-order Arabidopsis mutants lacking multiple B2 and B3 RAFs show ABA hyposensitivity. Our findings reveal a unique initiation and amplification mechanism of SnRK2 activation in ABA signaling in higher plants., SnRK2 kinase activity is rapidly activated in response to ABA. Here the authors show that initial activation of SnRK2s is achieved by B2 and B3 RAF kinase-mediated phosphorylation of the activation loop and that transphosphorylation between SnRK2s then amplifies the response.

Summary Plant stomata play a crucial role in leaf function, controlling water transpiration in response to environmental stresses and modulating the gas exchange necessary for photosynthesis. The phytohormone abscisic acid (ABA) promotes stomatal closure and inhibits light‐induced stomatal opening. The Arabidopsis thaliana E3 ubiquitin ligase COP1 functions in ABA‐mediated stomatal closure. However, the underlying molecular mechanisms are still not fully understood.Yeast two‐hybrid assays were used to identify ABA signaling components that interact with COP1, and biochemical, molecular and genetic studies were carried out to elucidate the regulatory role of COP1 in ABA signaling.The cop1 mutants are hyposensitive to ABA‐triggered stomatal closure under light and dark conditions. COP1 interacts with and ubiquitinates the Arabidopsis clade A type 2C phosphatases (PP2Cs) ABI/HAB group and AHG3, thus triggering their degradation. Abscisic acid enhances the COP1‐mediated degradation of these PP2Cs. Mutations in ABI1 and AHG3 partly rescue the cop1 stomatal phenotype and the phosphorylation level of OST1, a crucial SnRK2‐type kinase in ABA signaling.Our data indicate that COP1 is part of a novel signaling pathway promoting ABA‐mediated stomatal closure by regulating the stability of a subset of the Clade A PP2Cs. These findings provide novel insights into the interplay between ABA and the light signaling component in the modulation of stomatal movement.

In Arabidopsis, the plasma membrane transporter PUT3 is important to maintain the cellular homeostasis of polyamines and plays a role in stabilizing mRNAs of some heat-inducible genes. The plasma membrane Na+ /H+ transporter SOS1 and the protein kinase SOS2 are two salt-tolerance determinants crucial for maintaining intracellular Na+ and K+ homeostasis. Here, we report that PUT3 genetically and physically interacts with SOS1 and SOS2, and these interactions modulate PUT3 transport activity. Overexpression of PUT3 (PUT3OE) results in hypersensitivity of the transgenic plants to polyamine and paraquat. The hypersensitivity of PUT3OE is inhibited by the sos1 and sos2 mutations, which indicates that SOS1 and SOS2 are required for PUT3 transport activity. A protein interaction assay revealed that PUT3 physically interacts with SOS1 and SOS2 in yeast and plant cells. SOS2 phosphorylates PUT3 both in vitro and in vivo. SOS1 and SOS2 synergistically activate the polyamine transport activity of PUT3, and PUT3 also modulates SOS1 activity by activating SOS2 in yeast cells. Overall, our findings suggest that both plasma-membrane proteins PUT3 and SOS1 could form a complex with the protein kinase SOS2 in response to stress conditions and modulate the transport activity of each other through protein interactions and phosphorylation.

TPST is involved in fructose signaling to regulate the root development and expression of genes in biological processes including auxin biosynthesis and accumulation in Arabidopsis. Sulfonation of proteins by tyrosine protein sulfotransferases (TPST) has been implicated in many important biological processes in eukaryotic organisms. Arabidopsis possesses a single TPST gene and its role in auxin homeostasis and root development has been reported. Here we show that the Arabidopsis tpst mutants are hypersensitive to fructose. In contrast to sucrose and glucose, fructose represses primary root growth of various ecotypes of Arabidopsis at low concentrations. RNA-seq analysis identified 636 differentially expressed genes (DEGs) in Col-0 seedlings in response to fructose verses glucose. GO and KEGG analyses of the DEGs revealed that fructose down-regulates genes involved in photosynthesis, glucosinolate biosynthesis and IAA biosynthesis, but up-regulates genes involved in the degradation of branched amino acids, sucrose starvation response, and dark response. The fructose responsive DEGs in the tpst mutant largely overlapped with that in Col-0, and most DEGs in tpst displayed larger changes than in Col-0. Interestingly, the fructose up-regulated DEGs includes genes encoding two AtTPST substrate proteins, Phytosulfokine 2 (PSK2) and Root Meristem Growth Factor 7 (RGF7). Synthesized peptides of PSK-α and RGF7 could restore the fructose hypersensitivity of tpst mutant plants. Furthermore, auxin distribution and accumulation at the root tip were affected by fructose and the tpst mutation. Our findings suggest that fructose serves as a signal to regulate the expression of genes involved in various biological processes including auxin biosynthesis and accumulation, and that modulation of auxin accumulation and distribution in roots by fructose might be partly mediated by the TPST substrate genes PSK-α and RGF7.

Abiotic stresses and soil nutrient limitations are major environmental conditions that reduce plant growth, productivity and quality. Plants have evolved mechanisms to perceive these environmental challenges, transmit the stress signals within cells as well as between cells and tissues, and make appropriate adjustments in their growth and development in order to survive and reproduce. In recent years, significant progress has been made on many fronts of the stress signaling research, particularly in understanding the downstream signaling events that culminate at the activation of stress- and nutrient limitation-responsive genes, cellular ion homeostasis, and growth adjustment. However, the revelation of the early events of stress signaling, particularly the identification of primary stress sensors, still lags behind. In this review, we summarize recent work on the genetic and molecular mechanisms of plant abiotic stress and nutrient limitation sensing and signaling and discuss new directions for future studies.

Maintaining the structural integrity of the photosynthetic apparatus during dehydration is critical for effective recovery of photosynthetic activity upon rehydration in a variety of desiccation-tolerant plants, but the underlying molecular mechanism is largely unclear. The subaerial cyanobacterium Nostoc flagelliforme can survive extreme dehydration conditions and quickly recovers its photosynthetic activity upon rehydration. In this study, we found that the expression of the molecular chaperone NfDnaK2 was substantially induced by dehydration, and NfDnaK2 proteins were primarily localized in the thylakoid membrane. NfDnaJ9 was identified to be the cochaperone partner of NfDnaK2, and their encoding genes shared similar transcriptional responses to dehydration. NfDnaJ9 interacted with the NfFtsH2 protease involved in the degradation of damaged D1 protein. Heterologous expression of NfdnaK2 enhanced PSII repair and drought tolerance in transgenic Nostoc sp. PCC 7120. Furthermore, the nitrate reduction (NarL)/nitrogen fixation (FixJ) family transcription factors response regulator (NfRre1) and photosynthetic electron transport-dependent regulator (NfPedR) were identified as putative positive regulators capable of binding to the promoter region of NfdnaK2 and they may mediate dehydration-induced expression of NfdnaK2 in N. flagelliforme Our findings provide novel insights into the molecular mechanism of desiccation tolerance in some xerotolerant microorganisms, which could facilitate future synthetic approaches to the creation of extremophiles in microorganisms and plants.

Lysine-ε-acetylation (Kac) is a post-translational modification (PTM) that is critical for metabolic regulation and cell signaling in mammals. However, its prevalence and importance in plants remain to be determined. Employing high-resolution tandem mass spectrometry, we analyzed protein lysine acetylation in five representative Arabidopsis organs with 2 ~ 3 biological replicates per organ. A total of 2887 Kac proteins and 5929 Kac sites were identified. This comprehensive catalog allows us to analyze proteome-wide features of lysine acetylation. We found that Kac proteins tend to be more uniformly expressed in different organs, and the acetylation status exhibits little correlation with the gene expression level, indicating that acetylation is unlikely caused by stochastic processes. Kac preferentially targets evolutionarily conserved proteins and lysine residues, but only a small percentage of Kac proteins are orthologous between rat and Arabidopsis. A large portion of Kac proteins overlap with proteins modified by other PTMs including ubiquitination, SUMOylation and phosphorylation. Although acetylation, ubiquitination and SUMOylation all modify lysine residues, our analyses show that they rarely target the same sites. In addition, we found that “reader” proteins for acetylation and phosphorylation, i.e., bromodomain-containing proteins and GRF (General Regulatory Factor)/14-3-3 proteins, are intensively modified by the two PTMs, suggesting that they are main crosstalk nodes between acetylation and phosphorylation signaling. Analyses of GRF6/14-3-3λ reveal that the Kac level of GRF6 is decreased under alkaline stress, suggesting that acetylation represses plant alkaline response. Indeed, K56ac of GRF6 inhibits its binding to and subsequent activation of the plasma membrane H+-ATPase AHA2, leading to hypersensitivity to alkaline stress. These results provide valuable resources for protein acetylation studies in plants and reveal that protein acetylation suppresses phosphorylation output by acetylating GRF/14-3-3 proteins.

Soil salinity severely hampers agricultural productivity. Under salt stress, excess Na+ accumulation causes cellular damage and plant growth retardation, and membrane Na+ transporters play central roles in Na+ uptake and exclusion to mitigate these adverse effects. In this study, we performed sos1 suppressor mutant (named sup) screening to uncover potential genetic interactors of SOS1 and additional salt tolerance mechanisms. Map-based cloning and sequencing identified a group of mutants harboring dominant gain-of-function mutations in the vacuolar Na+/H+ antiporter gene AtNHX1. The gain-of-function variants of AtNHX1 showed enhanced transporter activities in yeast cells and increased salt tolerance in Arabidopsis wild type plants. Ion content measurements indicated that at the cellular level, these gain-of-function mutations resulted in increased cellular Na+ accumulation likely due to enhanced vacuolar Na+ sequestration. However, the gain-of-function suppressor mutants showed reduced shoot Na+ but increased root Na+ accumulation under salt stress, indicating a role of AtNHX1 in limiting Na+ translocation from root to shoot. We also identified another group of sos1 suppressors with loss-of-function mutations in the Na+ transporter gene AtHKT1. Loss-of-function mutations in AtHKT1 and gain-of-function mutations in AtNHX1 additively suppressed sos1 salt sensitivity, which indicates that the three transporters, SOS1, AtNHX1 and AtHKT1 function independently but coordinately in controlling Na+ homeostasis and salt tolerance in Arabidopsis. Our findings provide valuable information about the target amino acids in NHX1 for gene editing to improve salt tolerance in crops.

Maintenance of cell wall integrity is of great importance not only for plant growth and development, but also for the adaptation of plants to adverse environments. However, how the cell wall integrity is modulated under salt stress is still poorly understood. Here, we report that a nuclear-localized Agenet domain-containing protein SWO1 (SWOLLEN 1) is required for the maintenance of cell wall integrity in Arabidopsis under salt stress. Mutation in SWO1 gene results in swollen root tips, disordered root cell morphology, and root elongation inhibition under salt stress. The swo1 mutant accumulates less cellulose and pectin but more lignin under high salinity. RNA-seq and ChIP-seq assays reveal that SWO1 binds to the promoter of several cell wall-related genes and regulates their expression under saline conditions. Further study indicates that SWO1 interacts with importin ɑ IMPA1 and IMPA2, which are required for the import of nuclear-localized proteins. The impa1 impa2 double mutant also exhibits root growth inhibition under salt stress and mutations of these two genes aggravate the salt-hypersensitive phenotype of the swo1 mutant. Taken together, our data suggest that SWO1 functions together with importin ɑ to regulate the expression of cell wall-related genes, which enables plants to maintain cell wall integrity under high salinity.

Salicylic acid (SA) plays an important role for plant immunity, especially resistance against biotrophic pathogens. SA quickly accumulates after pathogen attack to activate downstream immunity events and is normally associated with a tradeoff in plant growth. Therefore, the SA level in plants has to be strictly controlled when pathogens are absent, but how this occurs is not well understood. Previously we found that in Arabidopsis (Arabidopsis thaliana), HISTONE DEACETYLASE 6 (HDA6), a negative regulator of gene expression, plays an essential role in plant immunity since its mutation allele shining 5 (shi5) exhibits autoimmune phenotypes. Here we report that this role is mainly through suppression of SA biosynthesis: first, the autoimmune phenotypes and higher resistance to Pst DC3000 of shi5 mutants depended on SA; second, SA significantly accumulated in shi5 mutants; third, HDA6 repressed SA biosynthesis by directly controlling the expression of CALMODULIN BINDING PROTEIN 60g (CBP60g) and SYSTEMIC ACQUIRED RESISTANCE DEFICIENT 1 (SARD1). HDA6 bound to the chromatin of CBP60g and SARD1 promoter regions, and histone H3 acetylation was highly enriched within these regions. Furthermore, the transcriptome of shi5 mutants mimicked that of plants treated with exogenous SA or attacked by pathogens. All these data suggest that HDA6 is vital for plants in finely controlling the SA level to regulate plant immunity.

Abscisic acid (ABA) signaling is critical for seed germination and abiotic stress responses in terrestrial plants. Pre-mRNA splicing is known to regulate ABA signaling. However, the involvement of canonical spliceosomal components in regulating ABA signaling is poorly understood. Here, we show that the spliceosome component Sm core protein SmEb plays an important role in ABA signaling. SmEb expression is up-regulated by ABA treatment, and analysis of Arabidopsis smeb mutant plants suggest that SmEb modulates the alternative splicing of the ABA signaling component HAB1 by enhancing the HAB1.1 splicing variant while repressing HAB1.2. Overexpression of HAB1.1 but not HAB1.2 rescues the ABA-hypersensitive phenotype of smeb mutants. Mutations in the transcription factor ABI3, 4, or 5 also reduce the ABA hypersensitivity of smeb mutants during seed germination. Our results show that the spliceosomal component SmEb plays an important role in ABA regulation of seed germination and early seedling development.

Mota Maradi is a sorghum line that exhibits holistic salinity tolerance mechanisms, making it a viable potential donor in breeding efforts for improved sorghum lines. High soil salinity is one of the global challenges for crop growth and productivity. Understanding the salinity tolerance mechanisms in crops is necessary for genetic breeding of salinity-tolerant crops. In this study, physiological and molecular mechanisms in sorghum were identified through a comparative analysis between a Nigerien salinity-tolerant sorghum landrace, Mota Maradi, and the reference sorghum line, BTx623. Significant differences on physiological performances were observed, particularly on growth and biomass gain, photosynthetic rate, and the accumulation of Na+, K+, proline, and sucrose. Transcriptome profiling of the leaves, leaf sheaths, stems, and roots revealed contrasting differentially expressed genes (DEGs) in Mota Maradi and BTx623 which supports the physiological observations from both lines. Among the DEGs, ion transporters such as HKT, NHX, AKT, HAK5, and KUP3 were likely responsible for the differences in Na+ and K+ accumulation. Meanwhile, DEGs involved in photosynthesis, cellular growth, signaling, and ROS scavenging were also identified between these two genotypes. Functional and pathway analysis of the DEGs has revealed that these processes work in concert and are crucial in elevated salinity tolerance in Mota Maradi. Our findings indicate how different complex processes work synergistically for salinity stress tolerance in sorghum. This study also highlights the unique adaptation of landraces toward their respective ecosystems, and their strong potential as genetic resources for future plant breeding endeavors.

Gene regulation is central for growth, development, and adaptation to environmental changes in all living organisms. Many genes are induced by environmental cues, and the expression of these inducible genes is often repressed under normal conditions. Here, we show that the SHINY2 (SHI2) gene is important for repressing salt-inducible genes and also plays a role in cold response. The shi2 mutant displayed hypersensitivity to cold, abscisic acid (ABA), and LiCl. Map-based cloning demonstrates that SHI2 encodes a DEAD- (Asp-Glu-Ala-Asp) box RNA helicase with similarity to a yeast splicing factor. Transcriptomic analysis of the shi2 mutant in response to cold revealed that the shi2 mutation decreased the number of cold-responsive genes and the magnitude of their response, and resulted in the mis-splicing of some cold-responsive genes. Under salt stress, however, the shi2 mutation increased the number of salt-responsive genes but had a negligible effect on mRNA splicing. Our results suggest that SHI2 is a component in a ready-for-transcription repressor complex important for gene repression under normal conditions, and for gene activation and transcription under stress conditions. In addition, SHI2 also serves as a splicing factor required for proper splicing of cold-responsive genes and affects 5' capping and polyadenylation site selection., The DEAD-box RNA helix SHI2 represses expression of salt-inducible genes and modulates splicing of cold-responsive genes. SHI2 participates in transcription and post-transcriptional processes in response to stress conditions.

Nitrogen (N) is critical for zinc (Zn) uptake into plant roots, which promotes Zn accumulation and biofortification of grains in winter wheat (Triticum aestivum L.). However, little is known about the role of TaZIPs genes in the Zn uptake and translocation in response to N supply. This study explored a possible avenue to improve Zn uptake and translocation by adjusting N supply in winter wheat. Winter wheat (Triticum aestivum.cv Zhengmai379) was cultivated with low, medium and high N in a nutrition solution or a pot soil with or without Zn supply. Plants in hydroponic culture were harvested at 21 d after different treatments and those in the soil culture were harvested at grain filling stage, and N and Zn concentrations and accumulation, Zn translocation coefficient, and the expression of TaZIP3 and TaZIP7 in different tissues were determined. When N supply was increased, Zn concentration and accumulation in shoot, Zn accumulation in whole plants, and root-to-shoot translocation of Zn were decreased in the solution without Zn supply. In the solution with Zn supply, increasing N supply increased Zn concentration in shoot, and medium N supply increased Zn accumulation in shoot and whole plants. Increasing N supply increased Zn concentration and accumulation in root, stem, leaf, glume and grain, and Zn translocation form root to stem, but decreased Zn translocation from stem to leaf, stem to glume and glume to grain under both Zn-deficient and Zn-sufficient conditions. Medium N supply up-regulated the expression of TaZIP3 and TaZIP7 in the roots of winter wheat cultured under both Zn-deficient and Zn-sufficient conditions. In Zn-deficient soil, the expression of TaZIP3 and TaZIP7 in root and glume was up-regulated but that in stem and leaf was down-regulated by increasing N supply. Medium or high N supply induced the expression of TaZIP3 and TaZIP7 in different tissues of winter wheat grown under Zn-sufficient condition. Adequate N supply improves the grain Zn concentration through enhancing Zn uptake and root-to-shoot translocation, which could be mediated by induced expression of TaZIP3 and TaZIP7 in roots of winter wheat.

The widespread agricultural problem of pre-harvest sprouting (PHS) could potentially be overcome by improving seed dormancy. Here, we report that miR156, an important grain yield regulator, also controls seed dormancy in rice. We found that mutations in one MIR156 subfamily enhance seed dormancy and suppress PHS with negligible effects on shoot architecture and grain size, whereas mutations in another MIR156 subfamily modify shoot architecture and increase grain size but have minimal effects on seed dormancy. Mechanistically, mir156 mutations enhance seed dormancy by suppressing the gibberellin (GA) pathway through de-represssion of the miR156 target gene Ideal Plant Architecture 1 (IPA1), which directly regulates multiple genes in the GA pathway. These results provide an effective method to suppress PHS without compromising productivity, and will facilitate breeding elite crop varieties with ideal plant architectures., Pre-harvest sprouting reduces the yield of agriculturally important crops such as rice. Here, the authors show that mutating specific members of the MIR156 gene family can suppress pre-harvest sprouting in rice without negative effects on plant architecture, suggesting a practical route to elite crop varieties.

Exposure to short-term cold stress influences disease resistance by mechanisms that remain poorly characterized. The molecular basis of cold-activated immunity was therefore investigated in Arabidopsis thaliana inoculated with the bacterial pathogen Pst DC3000, using a transcriptomic analysis. Exposure to cold stress for 10 hr was sufficient to activate immunity, as well as H2 O2 accumulation and callose deposition. Transcriptome changes induced by the 10-hr cold treatment were similar to those caused by pathogen infection, including increased expression of the salicylic acid (SA) pathway marker genes, PR2 and PR5, and genes playing positive roles in defence against (hemi)-biotrophs. In contrast, transcripts encoding jasmonic acid (JA) pathway markers such as PR4 and MYC2 and transcripts with positive roles in defence against necrotrophs were less abundant following the 10-hr cold treatment. Cold-activated immunity was dependent on SA, being partially dependent on NPR1 and ICS1/SID2. In addition, transcripts encoding SA biosynthesis enzymes such as ICS2, PAL1, PAL2, and PAL4 (but not ICS1/SID2) and MES9 were more abundant, whereas GH3.5/WES1 and SOT12 transcripts that encode components involved in SA modification were less abundant following cold stress treatment. These findings show that cold stress cross-activates innate immune responses via a SA-dependent pathway.

Background Cadmium (Cd) accumulation in crops will affect the yield and quality of crops, and also harm human health. The application of selenium (Se) can reduce the absorption and transport of Cd in winter wheat. Results The result showed that increasing Se supply significantly decreased Cd concentration and accumulation in shoots and roots of winter wheat, and the root to shoot translocation of Cd. The Se supply increased the root length, surface area and root volume, but decreased the root average diameter. Increasing Se supply significantly decreased Cd concentration in cell wall, soluble fraction and cell organelle in roots and shoots. An increase of Se supply inhibited Cd distribution in the organelle of shoot and root, but enhanced Cd distribution in the soluble fraction of shoot and the cell wall of root. The Se supply also decreased the proportion of active Cd (ethanol-extractable (FE) Cd and deionized water-extractable (FW) Cd) in roots. In addition, the expression of TaNramp5-a, TaNramp5-b, TaHMA3-a, TaHMA3-b and TaHMA2 were significantly increased with the increase of Cd concentration in roots, and the expression of TaNramp5-a, TaNramp5-b and TaHMA2 in roots were down-regulated by increasing Se supply, regardless of Se supply or Cd stress, respectively. The expression of TaHMA3-b in root was significantly down-regulated by Se10 treatment at both Cd5 and Cd25 but up-regulated by Se5 treatment at Cd25. The expression of TaNramp5-a, TaNramp5-b, TaHMA3-a, TaHMA3-b and TaHMA2 in shoot were down-regulated by increasing Se supply at Cd5, and Se5 treatment up-regulated the expression of those genes in shoot at Cd25. Conclusions The results confirm that Se application limit Cd accumulation in wheat via regulating subcellular distribution and the chemical forms of Cd in tissues of winter wheat, as well as the expression of TaNramp5-a, TaNramp5-b and TaHMA2 in root.

© 2020 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Domestication has resulted in reduced salt tolerance in tomato. To identify the genetic components causing this deficiency, we performed a genome‐wide association study (GWAS) for root Na(+)/K(+) ratio in a population consisting of 369 tomato accessions with large natural variations. The most significant variations associated with root Na(+)/K(+) ratio were identified within the gene SlHAK20 encoding a member of the clade IV HAK/KUP/KT transporters. We further found that SlHAK20 transports Na(+) and K(+) and regulates Na(+) and K(+) homeostasis under salt stress conditions. A variation in the coding sequence of SlHAK20 was found to be the causative variant associated with Na(+)/K(+) ratio and confer salt tolerance in tomato. Knockout mutations in tomato SlHAK20 and the rice homologous genes resulted in hypersensitivity to salt stress. Together, our study uncovered a previously unknown molecular mechanism of salt tolerance responsible for the deficiency in salt tolerance in cultivated tomato varieties. Our findings provide critical information for molecular breeding to improve salt tolerance in tomato and other crops.

Additional file 2: Figure S1. GO analysis of the DEGs between TB and ER. Figure S2. GO analysis of the DEGs between TB and FER. Figure S3. RT-qPCR detection of the selected DEGs among TB, ER and FER.

Additional file 1.

Terrestrial plants must cope with drought stress to survive. Under drought stress, plants accumulate the phytohormone abscisic acid (ABA) by increasing its biosynthesis and decreasing its catabolism. However, the regulatory pathways controlling ABA catabolism in response to drought remain largely unclear. Here, we report that the flowering repressor SHORT VEGETATIVE PHASE (SVP) is induced by drought stress and associates with the promoter regions of the ABA catabolism pathway genes CYP707A1, CYP707A3 and AtBG1, causing decreased expression of CYP707A1 and CYP707A3 but enhanced expression of AtBG1 in Arabidopsis leaves. Loss-of-function mutations in CYP707A1 and CYP707A3 or overexpression of AtBG1 could rescue the drought-hypersensitive phenotype of svp mutant plants by increasing cellular ABA levels. Collectively, our results suggest that SVP is a central regulator of ABA catabolism and that a regulatory pathway involving SVP, CYP707A1/3, and AtBG1 plays a critical role in plant response to water deficit and plant drought resistance.

MicroRNAs are 19- to 22-nucleotide small noncoding RNAs that have been implicated in abiotic stress responses. In this study, we found that knockdown of microRNA166, using the Short Tandem Target Mimic (STTM) system, resulted in morphological changes that confer drought resistance in rice (Oryza sativa). From a large-scale screen for miRNA knockdown lines in rice, we identified miR166 knockdown lines (STTM166); these plants exhibit a rolled-leaf phenotype, which is normally displayed by rice plants under drought stress. The leaves of STTM166 rice plants had smaller bulliform cells and abnormal sclerenchymatous cells, likely causing the rolled-leaf phenotype. The STTM166 plants had reduced stomatal conductance and showed decreased transpiration rates. The STTM166 lines also exhibited altered stem xylem and decreased hydraulic conductivity, likely due to the reduced diameter of the xylem vessels. Molecular analyses identified rice HOMEODOMAIN CONTAINING PROTEIN4 (OsHB4), a member of HD-Zip III gene family, as a major target of miR166; moreover, rice plants overexpressing a miR166-resistant form of OsHB4 resembled the STTM166 plants, including leaf rolling and higher drought resistance. The genes downstream of miR166-OsHB4 consisted of polysaccharide synthesis-related genes that may contribute to cell wall formation and vascular development. Our results suggest that drought resistance in rice can be increased by manipulating miRNAs, which leads to developmental changes, such as leaf rolling and reduced diameter of the xylem, that mimic plants’ natural responses to water-deficit stress.

In Arabidopsis, the plasma membrane transporter PUT3 is important to maintain the cellular homeostasis of polyamines and plays a role in stabilizing mRNAs of some heat-inducible genes. The plasma membrane Na

Abiotic stresses greatly affect the immunity of plants. However, it is unknown whether pathogen infection affects abiotic stress tolerance of host plants. Here, the effect of defense response on cold and heat tolerance of host plants was investigated in Pst DC3000-infected Arabidopsis plants, and it was found that the pathogen-induced defense response could alleviate the injury caused by subsequent cold and heat stress (38°C). Transcriptomic sequencing plus RT-qPCR analyses showed that some abiotic stress genes are up-regulated in transcription by pathogen infection, including cold signaling components ICE1, CBF1, and CBF3, and some heat signaling components HSFs and HSPs. Moreover, the pathogen-induced alleviation of cold and heat injury was lost in NahG transgenic line (SA-deficient), sid2-2 and npr1-1 mutant plants, and pathogen-induced expression of cold and heat tolerance-related genes such as CBFs and HSPs, respectively, was lost or compromised in these plants, indicating that salicylic acid signaling pathway is required for the alleviation of cold and heat injury by pathogen infection. In short, our current work showed that in fighting against pathogens, host plants also enhance their cold and heat tolerance via a salicylic acid-dependent pathway.

Drought is one of the most deleterious environmental conditions affecting crop growth and productivity. Here we report the important roles of a nuclear-encoded chloroplast protein, PsbP Domain Protein 5 (PPD5), in drought resistance in Arabidopsis (Arabidopsis thaliana). From a forward genetic screen, a drought-resistant mutant named ppd5-2 was identified, which has a knockout mutation in PPD5. The ppd5 mutants showed increased H(2)O(2) accumulation in guard cells and enhanced stomatal closure in response to drought stress. Further analysis revealed that the chloroplast-localized PPD5 protein interacts with and is phosphorylated by OST1, and phosphorylation of PPD5 increases its protein stability. Double mutant ppd5-2ost1-3 exhibited phenotypes resembling the ost1-3 single mutant with decreased stomatal closure, increased water loss, reduced H(2)O(2) accumulation in guard cells, and hypersensitivity to drought stress. These results indicate that the chloroplast protein PPD5 negatively regulates drought resistance by modulating guard cell H(2)O(2) accumulation via an OST1-dependent pathway. Interestingly, the thf1-1 mutant defective in the chloroplast protein THF1 displayed drought-resistance and H(2)O(2) accumulation similar to the ppd5 mutants, but the thf1-1ost1-3 double mutant resembled the phenotypes of the thf1-1 single mutant. These results indicate that both OST1-dependent and OST1-independent pathways exist in the regulation of H(2)O(2) production in chloroplasts of guard cells under drought stress conditions. Additionally, our findings suggest a strategy to improve plant drought resistance through manipulation of chloroplast proteins.

Summary: Plants respond to cold stress by inducing the expression of transcription factors that regulate downstream genes to confer tolerance to freezing. We screened an Arabidopsis transfer DNA (T-DNA) insertion library and identified a cold-hypersensitive mutant, which we named stch4 (sensitive to chilling 4). STCH4/REIL2 encodes a ribosomal biogenesis factor that is upregulated upon cold stress. Overexpression of STCH4 confers chilling and freezing tolerance in Arabidopsis. The stch4 mutation reduces CBF protein levels and thus delayed the induction of C-repeat-binding factor (CBF) regulon genes. Ribosomal RNA processing is reduced in stch4 mutants, especially under cold stress. STCH4 associates with multiple ribosomal proteins, and these interactions are modulated by cold stress. These results suggest that the ribosome is a regulatory node for cold stress responses and that STCH4 promotes an altered ribosomal composition and functions in low temperatures to facilitate the translation of proteins important for plant growth and survival under cold stress. : Yu et al. show that the ribosomal biogenesis factor STCH4 confers cold stress tolerance in Arabidopsis by maintaining rRNA processing and promoting CBF protein translation. The ribosome is likely a site for cold stress response. Keywords: cold stress, rRNA processing, STCH4, protein translation, CBF, ribosome