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We studied the D3-type cyclin function during gynoecium development in Arabidopsis and how they are related to the hormone cytokinin and the transcription factor SPATULA. Growth throughout the life of plants is sustained by cell division and differentiation processes in meristematic tissues. In Arabidopsis, gynoecium development implies a multiphasic process where the tissues required for pollination, fertilization, and seed development form. The Carpel Margin Meristem (CMM) is a mass of undifferentiated cells that gives rise to the gynoecium internal tissues, such as septum, ovules, placenta, funiculus, transmitting tract, style, and stigma. Different genetic and hormonal factors, including cytokinin, control the CMM function. Cytokinin regulates the cell cycle transitions through the activation of cell cycle regulators as cyclin genes. D3-type cyclins are expressed in proliferative tissues, favoring the mitotic cell cycle over the endoreduplication. Though the role of cytokinin in CMM and gynoecium development is highly studied, its specific role in regulating the cell cycle in this tissue remains unclear. Additionally, despite extensive research on the relationship between CYCD3 genes and cytokinin, the regulatory mechanism that connects them remains elusive. Here, we found that D3-type cyclins are expressed in proliferative medial and lateral tissues. Conversely, the depletion of the three CYCD3 genes showed that they are not essential for gynoecium development. However, the addition of exogenous cytokinin showed that they could control the division/differentiation balance in gynoecium internal tissues and outgrowths. Finally, we found that SPATULA can be a mechanistic link between cytokinin and the D3-type cyclins. The data suggest that the role of D3-type cyclins in gynoecium development is related to the cytokinin response, and they might be activated by the transcription factor SPATULA.

Background: Paphiopedilum orchids have a high ornamental value, and flower abundance is a key horticultural trait. Most Paphiopedilum plants exhibit weak tillering ability, with their tiller buds often entering a dormant state post-formation. Tiller production plays a crucial role in enhancing flower abundance and is potentially regulated by plant hormones. However, the effect of hormones on tillering in Paphiopedilum plants is still unclear. Results: In this study, we investigated the promotion of tillering in P. callosum through exogenous root irrigation of benzylaminopurine (BAP). We observed a dose-dependent promotion of tiller production by BAP, with the strongest effect observed at a concentration of 400 mg/L. By comparing the expression of key genes in P. 'SCBG Yingchun' (with strong tiller ability) and P callosum (with weak tiller ability), we found that BAP promotes tillering by interacting with abscisic acid (ABA). This interaction involves down-regulation of the ABA degradation gene PcCYP707A, leading to a reduction in ABA content, and the subsequent down-regulation of dormancy-associated genes (PcDRMH1, PcSVP) to release bud dormancy. Additionally, BAP promotes sustained outgrowth of tiller buds by increasing the level of indole-3-acetic acid (IAA) through up-regulation of the IAA synthesis gene PcYUC2 and the transport gene PcPINIC. Conclusions: Our results indicated that the application of BAP promotes lateral bud outgrowth and increases tiller production in P. callosum. Through transcriptome analysis, we found that the BAP-promotion of tillering involves not only changes in endogenous IAA, ABA, and CTKs content but is also associated with the regulation of metabolism-related genes and dormancy-associated genes. This study presents the first comprehensive report of BAP-promoted tillering in P. callosum, providing a foundational basis for further mechanistic studies on tiller development in Paphiopedilum species and other non-model plants. [ABSTRACT FROM AUTHOR]

Alfalfa is one of the primary forages, and its yield is largely dependent on the development of its leaf. In this study, to elucidate the mechanism of compound leaf development, we isolated and examined the alfalfa phenotype Chuancao No.7, exhibiting five leaflets. The agronomic traits of the Chuancao No.7 including the leaf blade area, leaf/stem ratio, total fresh weight, and dry weight showed significant increases compared to those of the wild-type. Analyses of forage quality traits indicated significant differences in crude protein (CP), acid detergent fiber (ADF), crude fat (CF), water-soluble sugars (WSS), carbon content, ash composition content, and phosphorus content between Chuancao No.7 alfalfa and wild-type. Transcriptomic profile analysis revealed that differentially expressed genes were identified in the cytokinin (CK) signaling pathway. Both exogenous treatment and endogenous CK content detection indicated that cytokinin played a key role in the development of the alfalfa compound leaf. These results serve as a valuable resource for optimizing the forage quality and exploring the excellent germplasm of alfalfa. [ABSTRACT FROM AUTHOR]

Cytokinins (CKs) are a class of phytohormones identified in the early 1960s and are mainly responsible for stimulating cell division. Following the discovery, research to help understand the pluralistic roles of CKs in plant growth and stress biology increased. With their fascinating ability, CKs serve as an important element in regulating the defense–growth trade-off. Herein, we demonstrate how the CK fine-tuning the organogenesis of different parts of horticultural plants is discussed. CK's role in tailoring reproductive biology (flowering, sex differentiation, fruit set, and fruit attributes) has been presented. An extensive explanation of the CK-mediated response of horticultural crops to abiotic (temperature, drought, and salinity) and biotic stresses (fungal, bacterial, and nematodes) is provided. Finally, we posit the unexplored roles of CKs and highlight the research gaps worth addressing. [ABSTRACT FROM AUTHOR]

In some mutualisms involving host plants, photoassimilates are provided as rewards to symbionts. Endophagous organisms often manipulate host plants to increase access to photoassimilates. Host manipulations by endophagous organisms that are also mutualists are poorly understood. We show host plant manipulations by symbionts and the role of phytohormones, i.e. the auxin indole-3-acetic acid (IAA), and the cytokinin trans-zeatin (tZ), in the brood-site pollination mutualism between fig trees and pollinator fig wasps. In this interaction, pollinator wasps pollinate Ficus flowers within an enclosed inflorescence called a syconium, in exchange for flowers that develop into galls nourishing pollinator offspring. To examine host manipulation by pollinator galls by affecting host fitness through seed reduction, we compared growth hormones released by syconial occupants within three experimentally produced treatment groups of syconia: S (containing only seeds), G (containing only pollinator galls) and SG (containing seeds and pollinator galls). We harvested syconia from each treatment in early and mid-phases of syconial maturation when maximal growth occurs and measured hormone levels. Hormones were reduced by mid-phase in general; however, their levels were mostly sustained in G syconia in the mid-phase, suggesting that galls manipulate the host to continuously access resources. We found no difference in IAA and tZ levels of S and G syconia. IAA concentrations were higher in SG syconia. From the perspective of the maintenance of mutualism, syconium volume and hormone concentrations were highest when both seeds and galls were present (SG treatment), indicating that both partners control allocation of resources to syconia. [ABSTRACT FROM AUTHOR]

Key message: Reducing endogenous CK levels accelerates fruit ripening in tomato by regulating ethylene biosynthesis and signalling pathway. Tomato is a typical climacteric fruit and is recognized as one of the most important horticultural crops globally. The ripening of tomato fruits is a complex process, highly regulated by phytohormones. Cytokinin (CK) is a hormone that primarily impacts the early development of fruit, however its influence on fruit ripening has not been thoroughly investigated. In this study, we used both wild-type Micro-Tom and transgenic tomato plants that overexpress AtCKX2, a CK degradation gene driven by the fruit-specific promoter Tfm7, to investigate the effect of CK on tomato fruit ripening. Our findings revealed that reducing endogenous CK levels in transgenic plants can accelerate the ripening process of tomato fruits. Premature activation of ethylene biosynthetic genes and ripening regulator genes was upregulated in CK-deficient fruits. Moreover, the application of exogenous ethylene inhibitors resulted in delayed fruit ripening in CK-deficient fruits. These results together suggest that CK plays a negative role in tomato fruit ripening by affecting the ethylene pathway. [ABSTRACT FROM AUTHOR]

Maxillaria picta is a Brazilian native orchid with a natural occurrence in the Atlantic Forest, a highly threatened and fragmented biodiversity hotspot. The in vitro culture is an excellent alternative for ex-situ orchid conservation and allows efficient plant propagation on a large scale. The 6-benzylaminopurine (BAP) is often used in in vitro culture to stimulate shoot formation. However, the morphoanatomical aspects of plantlets exposed to BAP and its residual effects remain unclear. Thus, we evaluated the morphoanatomical effects of BAP on in vitro culture and photosynthetic pigment concentration of M. picta acclimatized plants. Plantlets were obtained by in vitro seed germination and submitted to different concentrations of BAP, for 60 days. Roots and leaves were collected and morpho-anatomically evaluated. After 90 days of acclimatization, we quantified the photosynthetic pigments concentration of these plants. Our findings indicate that BAP supplementation significantly improves the formation of shoots and leaves, especially in treatment with 9 µM of BAP. However, concentrations above 9 µM of BAP increased tissue browning and significantly decreased the concentration of all photosynthetic pigments in acclimatized plants. Anatomically, 9 and 12 µM of BAP supplementation provided greater development of the vascular cylinder of the roots. Thus, this study provided new insights into the M. picta in vitro culture and showed the impact of BAP supplementation on the plantlets.Key message: BAP supplementation significantly improves the formation of shoots and leaves in M. picta in vitro plantlets despite presenting a negative correlation with photosynthetic pigment accumulation. [ABSTRACT FROM AUTHOR]

This study aimed to produce a premium herbal plant called Ammi visnaga (L.) Lam. that is continually gathered for medical uses. Under cover of darkness, seeds were sowed on sterile, moist filter paper. Nodal parts obtained from microshoots were first grown on a murashige and skoog (MS) medium free of hormones before being transferred into another MS medium supplemented with various concentrations of BA (6-benzyladenine), KIN (6-furfurylaminopurin), and 2iP (6- (γ,γ, dimethylallylamino) – purine) in conjunction with 0.1 mg/L 1-Naphthalenacetic acid (NAA). The medium with 0.5 mg/L BA had the maximum shoot multiplication, with the number of shoots (5.60 ± 0.87), whereas the media containing 1.5 mg/L KIN had the highest shoot length (9.60 ± 0.36 cm) and number of leaves/explant (22.00 ± 0.65). Young leaves that had been separated from the microshoots were utilized as explants to induce calli. Different concentrations of BA, KIN, and TDZ (Thiadiazuron) were evaluated for callus multiplication together with 2.0 mg/L 2,4-D. On a medium containing 2.0 mg/L 2,4-D in addition to 1.0 mg/L each of BA, KIN, and TDZ and 1.0 mg/L 2,4-D, the greatest callus growth was seen. However, in terms of overall callus multiplication, 1.0 mg/L BA in light conditions was the best. This research is a significant step toward mass-producing Ammi visnaga for further applications.Key message: The excessive exploitation of medicinal wild flora could be ceased and substituted with in vitro propagated specimens that possess equivalent or enhanced efficacy without environmental limitations in large quantities; please make reference to the supplementary video. [ABSTRACT FROM AUTHOR]

Panicle size is an important agronomic trait in rice, greatly influences the grain yield of rice (Oryza sativa L.). Although many panicle size genes have been reported, new panicle size controlling genes still need to be discovered. Here, we isolated two rice mutants, named Oryza sativa short panicle gene 3 (Osspg3), which displayed a semi-dwarf phenotype, shorter panicle, and smaller grain, thus, the number of grains per spike decreased. Inhibition of cell expansion of the Osspg3 mutants resulted in smaller grain size. We cloned Osspg3 by using map-based cloning combined with resequencing technique. OsSPG3 is highly expressed in the leaf sheath and panicle, and OsSPG3 protein is localized in the nucleus. Transcriptional analysis revealed antenna proteins photosynthesis, plant hormone signal transduction, plant mitogen-activated protein kinase (MAPK) signaling pathway, glycosaminoglycan degradation, glycosphingolipid biosynthesis and starch and sucrose metabolism were affected in the Osspg3 mutant. Moreover, the content of endogenous IAAs is significant decrease, but the content of endogenous cytokinin is significant increase. Our results indicating OsSPG3 is a key crosstalk factor of auxin and cytokinin pathway and providing a new potential gene resource for the improvement of rice panicle size. [ABSTRACT FROM AUTHOR]

Cytokinins (CKs) play important functions in plant growth and development and in response to adversity stress. However, little is known about the role CK plays in rice grain quality. We hypothesized that exogenous cytokinins could improve rice grain quality by regulating physiological traits and genes related to starch synthesis. Therefore, we exogenously applied different concentrations of kinetin (KT), an exogenous CK, during the grain-filling period. Our results show that all the different concentrations of exogenous KT treatments resulted in a significant increase in thousand-grain weight. In particular, chalkiness and chalky grain rate were significantly reduced, and gel consistency (GC) content and alkali spreading value (ASV) were significantly increased in 10−8 M KT treatment. Meanwhile, the exogenous application of 10−8 M KT positively affected the transcription of some starch synthesis-related genes, which was in contrast to the 10−5 M KT treatment. In conclusion, the exogenous application of appropriate concentrations of KT during the grain-filling period can ultimately affect rice grain quality by regulating the changes in the relevant indicators, such as appearance quality (AQ) and eating and cooking qualities (ECQ). [ABSTRACT FROM AUTHOR]

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Adventitious root (AR) formation is a bottleneck for vegetative proliferation. In this study, 13 AHP genes (MdAHPs) were identified in the apple genome. Phylogenetic analysis grouped them into 3 clusters (I, II, III), with 4, 4, and 5 genes respectively. The 13 MdAHPs family members were named MdAHP1 to MdAHP13 by chromosome positions. The physicochemical properties, phylogenetic relationship, motifs, and elements of their proteins were also analyzed. The amino acid quantity varied from 60~189 aa, isoelectric point lay between 4.10 and 8.93, and there were 3~7 protein-conserving motifs. Excluding MdAHP6 , other members' promoter sequences behaved 2-4 CTK response elements. Additionally, the expression characteristics of MdAHPs family members at key stages of AR formation and in different tissues were also examined with exogenous 6-BA and Lov treatments. The results showed that MdAHP3 might be a key member in AR formation. GUS staining indicated that the activity of the MdAHP3 promoter was also significantly enhanced by CTK treatment. The protein interactions of MdAHP3/MdAHP1 and MdAHP3/MdAHP6 were verified. Compared with WT, 35S::MdAHP3 transgenic poplars inhibited AR formation. The above experimental results suggested that MdAHP3, as a key family member, interacts with MdAHP1 and MdAHP6 proteins to jointly mediate AR formation in apple rootstocks. [ABSTRACT FROM AUTHOR]

Adenine metabolism is important for common bean (Phaseolus vulgaris L.) productivity since this legume uses ureides derived from the oxidation of purine nucleotides as its primary nitrogen storage molecules. Purine nucleotides are produced from de novo synthesis or through salvage pathways. Adenine phosphoribosyl transferase (APRT) is the enzyme dedicated to adenine nucleobase salvage for nucleotide synthesis, but it can also convert active cytokinin bases into their inactive nucleotide forms. In common bean, APRT is encoded by four genes. Gene expression analysis, biochemical properties, and subcellular location indicated functional differences among the common bean APRT isoforms. CRISPR/Cas9 targeted down-regulation of two of the four PvAPRTs followed by metabolomic and physiological analyses of targeted hairy roots revealed that, although the two proteins have redundant functions, PvAPRT1 mostly participated in the salvage of adenine, whereas PvAPRT5 was the predominant form in the regulation of cytokinin homeostasis and stress responses with a high impact in root and nodule growth. [ABSTRACT FROM AUTHOR]

Objective: Kochia is recently used as a forage and medicinal plant resistant to environmental stresses such as salinity and drought. One of the techniques used in biotechnology and plant breeding is tissue culture. Methods: Based on this, callus formation and regeneration of Kochia under the influence of hormonal factors and explants types was conducted in a factorial experiment on a completely randomized design with hormonal treatments (9 levels) and explants (3 levels) in 5 replications. After 70 days, the explants were examined for different traits and determined the most suitable explant for callus production. Results: According to the results regarding changes in the percentage of leaf callus formation, the greatest increase was in MS + 0.5 mg/l Kin + 1 mg/l NAA treatment. For callus formation and percentage of direct rooting, there is a significant difference between leaf explants, cotyledon and hypocotyl. But for the percentage of direct regeneration and the percentage of shoot formation, a significant difference has been observed between the leaf explant with cotyledon and the hypocotyl. The results showed that the highest degree of callus formation occurred in the treatment of MS +0.5 mg/l Kin + 1 mg/l NAA in the leaf and the axis of the cotyledon, and then in the treatments MS + 1 mg/l NAA and MS + 0.05 mg/l BA + 0.5 mg/l NAA is in the organs of cotyledon and the hypocotyl. Conclusion: Finally, 2,4-D could lead to more callus formation of the Kochia and it was observed that no callus formation was done in treatments without hormones. Although, to optimize callus formation and regeneration in this plant, it is suggested to also test the effects of environmental variables such as temperature, humidity, and photoperiod, and different levels of growth hormones such as IBA and GA3. [ABSTRACT FROM AUTHOR]

Abstract Background The mutualistic beneficial relationship between legume plants and rhizobia enables the growth of plants in nitrogen-limiting conditions. Rhizobia infect legumes through root hairs and trigger nodule organogenesis in the cortex. The plant hormone cytokinin plays a pivotal role in regulating both rhizobial infection and the initiation of nodule development. However, the mechanism used by the cytokinin output module to control symbiosis remains poorly documented. Results In this study, we identified a cytokinin signaling output component encoded by the Type-B RESPONSE REGULATOR (RRB) gene, LjRRB12, which is expressed in Lotus japonicus nodule primordia and young nodules. Disruption of LjRRB12 leads to a reduction in nodulation and to an increase in the number of infection threads. Overexpression of LjRRB12D76E, an active form of the LjRRB12 protein, induces nodule-like structures in wild type and hit1 (hyperinfected 1/lotus histidine kinase 1) mutants but not in nin2 (nodule inception 2) mutants. Additionally, we utilized nCUT&Tag and EMSA to demonstrate that LjRRB12 can bind a CE (cytokinin response element) from the LjNIN promoter. Conclusions Our results provide a deeper understanding of nodule organogenesis by establishing a link between the cytokinin signal and the transcriptional regulation of LjNIN.

Abstract Background Ascophyllum Nodosum (L.) Extracts (ANE), even at low concentrations, are reported to behave as plant growth promoters and inducers of resistance to diverse abiotic and biotic stresses. However, the mechanisms regulating ANE's actions on plant metabolism have not been fully described. This study has two main objectives: (1) to investigate the role of some of the main components of an ANE extract on the plant growth-promoting action of ANE in Arabidopsis thaliana. To this end, experiments have been carried out studying the effect on plant growth of some of the main components of ANE at the concentration contained in the application rate of ANE extract. This study will allow us to obtain some insights about whether the ANE´s action may be ascribed to one or several of its components or derives from the ANE`s action as a whole and (2) to investigate the role of the signaling pathways regulated by salicylic acid (SA), indolacetic acid (IAA), and cytokinins (CK) in the mechanism of action behind the plant growth-promoting action of ANE. To this end, three Arabidopsis thaliana lines affected by the action of SA were treated with ANE: two loss-of-function mutants, pad4 (Phytoalexin Deficient 4) and sid2-2 (Salicylic acid Induction Deficient), along with a transgenic line expressing a bacterial salicylate hydroxylase, nahg, that prevents SA accumulation. ANE was also tested in an IAA loss-of-function mutant (tir1) and two CK receptors loss-of-function mutants (ahk2 and ahk3). Thus, the research advanced in the ANE´s mediated shoot growth-promoting mechanism of action through the coordinated signaling network involving SA-, CK-, and IAA-signaling pathways. Results The results revealed that: (1) the plant growth-promoting action of ANE seems to be related to the interaction of its components rather than to the action of some of its components and (2) the nahg transgenic line and the sid2-2 mutation, blocked the capacity of ANE to stimulate shoot growth. However, the pad4 mutant was stimulated by ANE. The fact that the action of ANE is impaired in sid2-2 and nahg indicates that the shoot growth-promoting effect of ANE is dependent on the SA-regulated signaling pathway. Likewise, the application of ANE to tir1, ahk2, and ahk3 plant mutants also affected the ANE´s capacity to promote shoot growth. Conclusions These results indicate that the ANE`s ability to stimulate shoot growth involves the coordinated activation of salicylic acid-, cytokinin-, and auxin-signaling pathways. The results obtained in the pad4 mutant indicate that the ANE´s action through the SA-signaling pathways that promote shoot growth differs from those regulated by the Enhanced Disease Susceptibility1/Phytoalexin Deficient4 (EDS1/PAD4) system. Finally, the action of ANE1 promoting plant growth seems to derive from the action of the extract as a whole. Graphical Abstract

Abstract Hyperhydricity is the most extensive physiological disorder during in vitro propagation. This disturbance can induce anatomical, morphological and physiological problems that cause serious damage. The factors that cause hyperhydricity are the composition of nutrient media and cultures conditions. To reduce the hyperhydricity of Pistacia khinjuk, ammonium nitrate (NH4NO3), calcium chloride (CaCl2·2H2O), cytokinins of meta-topolin (mT) and 6-benzylaminopurine (BAP) at different concentrations were investigated in Murashige and Skoog (MS) medium. The lowest percentage of hyperhydricity (34.30%) were obtained from the medium containing 1650 mg/L NH4NO3, 110 mg/L CaCl2·2H2O and1 mg/L mT; the highest percentage of hyperhydricity (68.42%) were obtained from the medium containing 206.25 mg/L NH4NO3, 440 mg/L CaCl2·2H2O and 0.5 mg/L BAP. The maximum average number of shoots per explant (2.45), average shoots length (18.47 mm) and proliferation rate (85%) were obtained from the medium containing 1650 mg/L NH4NO3, 110 mg/L CaCl2·2H2O of MS and 1 mg/L mT. In addition, when soluble protein (2.12 mg/g) and total chlorophyll a, b (0.96 mg/g) value of normal (non-hyperhydric) shoots were higher than hyperhydric shoots, carotenoid (11.75 µg /g) and water content (78.70%) value of normal shoots were lower than hyperhydric shoots. This study concludes that the hyperhydricity percentage of in vitro P. khinjuk shoots was reduced (12.8%) on modified MS medium with NH4NO3, CaCl2·2H2O and mT according to standard MS medium.

Abstract Background Plant breeding played a very important role in transforming strawberries from being a niche crop with a small geographical footprint into an economically important crop grown across the planet. But even modern marker assisted breeding takes a considerable amount of time, over multiple plant generations, to produce a plant with desirable traits. As a quicker alternative, plants with desirable traits can be raised through tissue culture by doing precise genetic manipulations. Overexpression of morphogenic regulators previously known for meristem development, the transcription factors Growth-Regulating Factors (GRFs) and the GRF-Interacting Factors (GIFs), provided an efficient strategy for easier regeneration and transformation in multiple crops. Results We present here a comprehensive protocol for the diploid strawberry Fragaria vesca Hawaii 4 (strawberry) regeneration and transformation under control condition as compared to ectopic expression of different GRF4-GIF1 chimeras from different plant species. We report that ectopic expression of Vitis vinifera VvGRF4-GIF1 provides significantly higher regeneration efficiency during re-transformation over wild-type plants. On the other hand, deregulated expression of miRNA resistant version of VvGRF4-GIF1 or Triticum aestivum (wheat) TaGRF4-GIF1 resulted in abnormalities. Transcriptomic analysis between the different chimeric GRF4-GIF1 lines indicate that differential expression of FvExpansin might be responsible for the observed pleiotropic effects. Similarly, cytokinin dehydrogenase/oxygenase and cytokinin responsive response regulators also showed differential expression indicating GRF4-GIF1 pathway playing important role in controlling cytokinin homeostasis. Conclusion Our data indicate that ectopic expression of Vitis vinifera VvGRF4-GIF1 chimera can provide significant advantage over wild-type plants during strawberry regeneration without producing any pleiotropic effects seen for the miRNA resistant VvGRF4-GIF1 or TaGRF4-GIF1.

Background: Ascophyllum Nodosum (L.) Extracts (ANE), even at low concentrations, are reported to behave as plant growth promoters and inducers of resistance to diverse abiotic and biotic stresses. However, the mechanisms regulating ANE's actions on plant metabolism have not been fully described. This study has two main objectives: (1) to investigate the role of some of the main components of an ANE extract on the plant growth-promoting action of ANE in Arabidopsis thaliana. To this end, experiments have been carried out studying the effect on plant growth of some of the main components of ANE at the concentration contained in the application rate of ANE extract. This study will allow us to obtain some insights about whether the ANE´s action may be ascribed to one or several of its components or derives from the ANE's action as a whole and (2) to investigate the role of the signaling pathways regulated by salicylic acid (SA), indolacetic acid (IAA), and cytokinins (CK) in the mechanism of action behind the plant growth-promoting action of ANE. To this end, three Arabidopsis thaliana lines affected by the action of SA were treated with ANE: two loss-of-function mutants, pad4 (Phytoalexin Deficient 4) and sid2-2 (Salicylic acid Induction Deficient), along with a transgenic line expressing a bacterial salicylate hydroxylase, nahg, that prevents SA accumulation. ANE was also tested in an IAA loss-of-function mutant (tir1) and two CK receptors loss-of-function mutants (ahk2 and ahk3). Thus, the research advanced in the ANE´s mediated shoot growth-promoting mechanism of action through the coordinated signaling network involving SA-, CK-, and IAA-signaling pathways. Results: The results revealed that: (1) the plant growth-promoting action of ANE seems to be related to the interaction of its components rather than to the action of some of its components and (2) the nahg transgenic line and the sid2-2 mutation, blocked the capacity of ANE to stimulate shoot growth. However, the pad4 mutant was stimulated by ANE. The fact that the action of ANE is impaired in sid2-2 and nahg indicates that the shoot growth-promoting effect of ANE is dependent on the SA-regulated signaling pathway. Likewise, the application of ANE to tir1, ahk2, and ahk3 plant mutants also affected the ANE´s capacity to promote shoot growth. Conclusions: These results indicate that the ANE's ability to stimulate shoot growth involves the coordinated activation of salicylic acid-, cytokinin-, and auxin-signaling pathways. The results obtained in the pad4 mutant indicate that the ANE´s action through the SA-signaling pathways that promote shoot growth differs from those regulated by the Enhanced Disease Susceptibility1/Phytoalexin Deficient4 (EDS1/PAD4) system. Finally, the action of ANE1 promoting plant growth seems to derive from the action of the extract as a whole. [ABSTRACT FROM AUTHOR]

Legumes have the capability to form nodules that facilitate symbiotic nitrogen fixation (SNF) with rhizobia. Given the substantial energy consumption during the process of SNF, legumes need to optimize nodule number in response to everchanging environmental scenarios. The TGACG BINDING FACTOR1/4 (TGA1/4) are key players in the basal immune response of plants. In this study, both β-glucuronidase staining and quantitative reverse transcription PCR (qRT-PCR) demonstrated that both GmbZIP4a and GmbZIP4b are inducible upon rhizobial inoculation. To investigate their roles further, we constructed gmbzip4a/b double mutants using CRISPR/Cas9 system. Nodulation assessments revealed that these double mutants displayed a reduction in the number of infection threads, which subsequently resulted in a decreased nodule number. However, the processes associated with nodule development including nodule fresh weight, structural characteristics, and nitrogenase activity, remained unaffected in the double mutants. Subsequent transcriptome analyses revealed that zeatin biosynthesis was downregulated in gmbzip4a/b mutants post rhizobial inoculation. Supporting these findings, genes associated with cytokinin (CTK) signaling pathway were upregulated in Williams 82 (Wm82), but this upregulation was not observed in the double mutants after rhizobial treatment. These results suggest that GmbZIP4a/b positively influences nodule formation by promoting the activation of the CTK signaling pathway during the early stages of nodule formation. [ABSTRACT FROM AUTHOR]

Background: The mutualistic beneficial relationship between legume plants and rhizobia enables the growth of plants in nitrogen-limiting conditions. Rhizobia infect legumes through root hairs and trigger nodule organogenesis in the cortex. The plant hormone cytokinin plays a pivotal role in regulating both rhizobial infection and the initiation of nodule development. However, the mechanism used by the cytokinin output module to control symbiosis remains poorly documented. Results: In this study, we identified a cytokinin signaling output component encoded by the Type-B RESPONSE REGULATOR (RRB) gene, LjRRB12, which is expressed in Lotus japonicus nodule primordia and young nodules. Disruption of LjRRB12 leads to a reduction in nodulation and to an increase in the number of infection threads. Overexpression of LjRRB12D76E, an active form of the LjRRB12 protein, induces nodule-like structures in wild type and hit1 (hyperinfected 1/lotus histidine kinase 1) mutants but not in nin2 (nodule inception 2) mutants. Additionally, we utilized nCUT&Tag and EMSA to demonstrate that LjRRB12 can bind a CE (cytokinin response element) from the LjNIN promoter. Conclusions: Our results provide a deeper understanding of nodule organogenesis by establishing a link between the cytokinin signal and the transcriptional regulation of LjNIN. [ABSTRACT FROM AUTHOR]

In reaction to a stimulus, signaling molecules are made, generate a response, and are then degraded. Nucleotides are classically associated with central metabolism and nucleic acid biosynthesis, but there are a number of nucleotides and nucleotide derivatives in plants to which this simple definition of a signaling molecule applies in whole or at least in part. These include cytokinins and chloroplast guanosine tetraposphate (ppGpp), as well as extracellular canonical nucleotides such as extracellular ATP (eATP) and NAD+ (eNAD+). In addition, there is a whole series of compounds derived from NAD+ such as ADP ribose (ADPR), and ATP–ADPR dinucleotides and their hydrolysis products (e.g. pRib-AMP) together with different variants of cyclic ADPR (cADPR, 2´-cADPR, 3´-cADPR), and also cyclic nucleotides such as 3´,5´-cAMP and 2´,3´-cyclic nucleoside monophosphates. Interestingly, some of these compounds have recently been shown to play a central role in pathogen defense. In this review, we highlight these exciting new developments. We also review nucleotide derivatives that are considered as candidates for signaling molecules, for example purine deoxynucleosides, and discuss more controversial cases. [ABSTRACT FROM AUTHOR]

Summary Sheath blight (ShB), caused by Rhizoctonia solani, is a highly destructive disease in many crops worldwide and no major resistance genes are available. Here, we identified a sbr1 (sheath blight resistance 1) rice mutant, which shows enhanced ShB resistance and maintains wildtype agronomic traits including yield, but carries an undesired stay‐green phenotype. Through map‐based cloning and transgenic validation, we found that an insertion disrupting the Stay‐Green (OsSGR) gene is responsible for sbr1 phenotypes. Mechanistically, the sbr1/Ossgr mutants reduce the expression of most OsCKX genes, which function in cytokinin (CK) degradation, to accumulate CK leading to ShB resistance. Importantly, knockout of OsCKX7, predominantly expressed in the leaf sheath and highly induced by R. solani, significantly enhances ShB resistance without stay‐green phenotype nor yield penalty, showing high application potential. Thus, our study reveals novel insights that OsSGR and cytokinin play key roles in rice‐R. solani interaction and generates a valuable ShB‐resistant germplasm. [ABSTRACT FROM AUTHOR]

Robustness is the invariant development of phenotype despite environmental changes and genetic perturbations. In the Arabidopsis flower bud, four sepals robustly initiate and grow to a constant size to enclose and protect the inner floral organs. We previously characterized the mutant development-related myb-like 1 (drmy1), where 3–5 sepals initiate variably and grow to different sizes, compromising their protective function. The molecular mechanism underlying this loss of robustness was unclear. Here, we show that drmy1 has reduced TARGET OF RAPAMYCIN (TOR) activity, ribosomal content, and translation. Translation reduction decreases the protein level of ARABIDOPSIS RESPONSE REGULATOR7 (ARR7) and ARABIDOPSIS HISTIDINE PHOSPHOTRANSFER PROTEIN 6 (AHP6), two cytokinin-signaling inhibitors that are normally rapidly produced before sepal initiation. The resultant upregulation of cytokinin signaling disrupts robust auxin patterning and sepal initiation. Our work shows that the homeostasis of translation, a ubiquitous cellular process, is crucial for the robust spatiotemporal patterning of organogenesis. [Display omitted] • DRMY1 promotes TOR signaling and protein synthesis in Arabidopsis • High synthesis of ARR7 and AHP6 dampens cytokinin signaling in the floral meristem • Low cytokinin signaling promotes robust auxin patterning and sepal initiation • High cytokinin signaling in drmy1 mutant may maintain protein synthesis homeostasis Developmental robustness is when organs develop to reproducible size, number, and arrangement, which Kong and Zhu et al. studied in sepals of the Arabidopsis plant. A transcription factor, DRMY1, maintains TOR signaling and translation, allowing strong synthesis of proteins key to robust hormone patterning and, thus, robust organogenesis. [ABSTRACT FROM AUTHOR]

Cytokinin signalling plays both positive and negative roles in plant resistance to pathogens. It is not clear whether the role of cytokinin changes at the different stages of pathogen infection. Arabidopsis thaliana sequentially exhibits distinct root morphological symptoms during Ralstonia solanacearum infection, which offers a good system to investigate function of cytokinin in the whole pathogen infection process. Using this system, we found increase of cytokinin signalling by Lonely Guy 2 (LOG2) overexpression or depletion of type‐A Arabidopsis Response Regulators (ARRs), negative regulators of cytokinin signalling pathway, promoted cell death, wilting symptom and bacterial growth, but attenuated primary root growth inhibition and lateral root formation. The decrease of cytokinin signalling by mutation on Isopentenyl Transferases (IPTs) inhibited root hair formation, cell death, wilting symptom and bacterial colonisation. Application of different concentration of exogenesis 6‐benzylaminopurine (6‐BA) showed first promoted, then decreased root hair formation. Moreover, application of 6‐BA accelerated cell death but suppressed lateral root formation and primary root growth inhibition. The diverse roles of cytokinin in these different root disease phenotypes suggested function of cytokinin during plant responses to R. solanacearum is cell type‐specific, which provides new insights on roles of cytokinin signalling in regulation on plant–pathogen interactions. [ABSTRACT FROM AUTHOR]

Vanda limbata is one of the most popular ornamental orchids. Currently, its growth is slow, making it necessary to improve its cultivation techniques. One of the possible ways to achieve this is to use plant growth regulator (PGR) treatment. Thidiazuron (TDZ) is a cytokinin used to increase the growth of V. limbata. This study aimed to determine the effect of TDZ concentration on the growth rate of V. limbata. The study involved cultivating V. limbata on planting media and spraying it with TDZ at various concentrations. This research uses a CRD (Completely Randomized Design) singlefactor, which is TDZ concentration at three concentrations (factor levels) of 0, 25, and 50 ppm. Data were analyzed using analysis of variance and Duncan's Multiple Range Test at 5% significance level. The study ran for three months and the following response variables were measure: the number of new leaves, increase in length of old leaves, length of new leaves, increase in width of old leaves, width of new leaves, number of roots, and stomatal density. The results showed that TDZ significantly increased leaf length and the number of new leaves of V. limbata, but decreased the density of stomata. Thidiazuron at 50 ppm was the best treatment for increasing the growth of V. limbata. [ABSTRACT FROM AUTHOR]

In the in vitro cloning of specific individuals of woody species, a challenge can be the low viability of explants collected from old mature donor trees due to the recalcitrance of their plant material. Other factors, such as the auxin–cytokinin balance, must also be considered. We investigated how in vitro conditions and donor age can modulate the regeneration capacity, morphophysiology, and DNA methylation of Quercus robur. Explants from two different donors (70- and 600-year-old trees) were subjected to 8 different treatments, which consisted of 0, 1.25, 3.5, or 7.0 µM 6-benzylaminopurine (BAP) combined with two concentrations of 0 or 0.5 µM 1-naphthaleneacetic acid (NAA). In the absence of BAP, there was no shoot induction, and root formation was achieved only in the shoots of the 70-year-old clone. Shoot number was lower in the shoots of the 600-year-old clone. Both clones showed increased regeneration capacity under BAP exposure, which was positively correlated with 8-hydroxydeoxyguanosine (8-oxo-dG) levels and the antioxidant capacity of total phenolics. In contrast, shoot induction was negatively correlated with 5-methylcytosine (m5C) levels. Treatments with increased BAP concentrations induced the development of anatomical and biochemical characteristics such as underdeveloped tissues and/or delayed tissue development, and this effect was less intense in the 600-year-old clone. Global hypomethylation strongly correlates with guanine hyperoxidation and the de novo regeneration response. Our results suggest that explants collected from fully mature trees may have different growth regulator supplementation needs due to the ‘donor age’ factor. Older clones may require a higher concentration of cytokinins to ensure a regenerative response.Key message: Global hypomethylation strongly correlates with the de novo regeneration response. BAP can reduce the 5-methylcytosine levels during in vitro multiplication. BAP altered the antioxidant capacity and 8-hydroxydeoxyguanosine levels of explants. [ABSTRACT FROM AUTHOR]

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Tiller development is regulated by genetics, endogenous hormones, and environmental factors. In this study, rice seedlings from four upland and two lowland rice varieties that were treated with 1.0 mg L− 1 kinetin (a synthetic cytokinin) in vitro could produce additional tillers as early as 20 to 30 days after transplanting, compared to the untreated rice seedlings. However, the number of tillers of kinetin-treated upland rice varieties (Bokilong and Gonsulak) grown in greenhouse did not increase although they developed the first tiller 8 to 9 days earlier than the untreated seedlings. In addition, two lowland rice varieties (Kadaria and MR269) grown in upland growth condition produced 73.7% and 46.5% less tillers, respectively, compared to lowland growth condition; possibly due to an increase of abscisic acid and a lower ratio of trans-zeatin to indole acetic acid. Understanding the effects of kinetin to tiller development in rice may help to increase the total number of tillers and yield of upland rice varieties. [ABSTRACT FROM AUTHOR]

This study investigates the mechanisms driving maize compensatory growth upon post-drought, to reveal how the root's original cytokinins are regulated by the two-fold roles of heterotrophic bacteria with ammonia-oxidizing (HAOB) capabilities. The HAOB' dual roles encompass influencing root cytokinin synthesis and transport through nitrification and a direct pathway. Experiment 1 involved introducing the application of varying amounts of NO3− to the roots to examine how nitrification affects cytokinin roots-to-leaves transport. Results demonstrate that the 30–40 mmol·L−1 NO3− concentration had ideal effects on enhancing post-drought growth in maize by facilitating cytokinin synthesis and transport. In experiment 2, an HAOB strain, S2_8_1, was utilized and NO3− was supplemented alongside HAOB inoculation to assess the joint impacts of nitrification and the direct pathway on the production and transportation of cytokinins. Results demonstrate that the HAOB strain S2_8_1 increases nitrification rates in rhizosphere soil, thereby promoting the transport of cytokinins from roots to leaves. In addition, the HAOB strain promotes root cytokinin transport to leaves autonomously, showcasing its direct pathway. Inoculation with the HAOB strain increased leaf cytokinin content and improved water use efficiency compared to the addition of NO3−; however, the combination of NO3− and HAOB strains resulted in a synergistic effect and further improvement. These findings elucidate how HAOB can enhance maize compensatory growth through its dual roles, presenting promising applications in agriculture. [ABSTRACT FROM AUTHOR]

Pisonia grandis R. Br. is a tree commonly found in urban coastal and tropical regions, valued for its ornamental beauty and utility in agroforestry and traditional medicine. To facilitate its propagation, particularly through in vitro techniques, this study aimed to refine a propagation system by inducing adventitious buds from node explants of mature tree. The study revealed that the Murashige and Skoog (MS) medium, supplemented with 30 g L−1 sucrose and 2.0 mg L−1 thidiazuron (TDZ), effectively stimulated bud break. Furthermore, a combination of 1.0 mg L−1 TDZ and 0.5 mg L−1 α-naphthalene acetic acid (NAA) yielded optimal shoot multiplication, resulting in an average of 16.0 shoots per explant with a length of 5.9 cm. In contrast, utilizing 1.0 mg L−1 6-benzylaminopurine (BAP) and 0.5 mg L−1 NAA led to producing 10.0 shoots with a height of 3.7 cm. Incorporating TDZ significantly enhanced shoot numbers, size, and overall health of the shootlets. Microscopic analysis revealed that leaves and petioles derived from the TDZ and NAA combination exhibited desirable features, such as a thick cuticle, well-differentiated epidermis, mesophyll, vascular tissues, stomata, and improved vein density compared to those derived from BAP and NAA. The maximum root percentage (87.5%) and adventitious root formation (averaging 8.0 roots with a length of 6.2 cm) were observed on half-strength media supplemented with 1.5 mg L−1 indole-3-butyric acid (IBA). Conversely, NAA fortification resulted in lower rooting percentages (77.8% response with an average of 4.7 roots measuring 4.0 cm in length). Subsequently, the rooted plantlets were successfully acclimatized using a mixture of soilrite®, cocopeat, and garden soil (1:1:1 v/v ratio), with a survival rate of 92.0% in the field. This study contributes valuable insights into the optimized use of growth regulators for the large-scale propagation of P. grandis and related species, ensuring the production of micro-morpho-structurally stable plantlets. [ABSTRACT FROM AUTHOR]

Cytokinins (CKs) not only promote the growth of female flowers in industrial hemp but also serve as plant hormones that influence leaf development and regulate various genes, including transcription factors. The molecular mechanism of cytokinin response in industrial hemp leaves remains unclear. In this study, industrial hemp Longma 5 was utilized, with 60 mg·L− 1 and 120 mg·L− 1 of 6-BA sprayed at the three-leaf stage, followed by transcriptome sequencing at the mature stage. 3244 DEGs were identified in the Ctrl (control) vs. B60 (60 mg·L− 1 6-BA treatment) group, including 1714 upregulated genes and 1530 downregulated genes; 7818 DEGs were identified in the Ctrl vs. B120 (120 mg·L− 1 6-BA treatment) group, including 3772 upregulated genes and 4046 downregulated genes. Further analysis showed that these DEGs were primarily enriched in pathways associated with metabolism and energy, including photosynthesis, photosynthesis-antenna protein, and phenylpropanoid biosynthesis. The CTK, auxin, ABA, GA, ETH and JA signaling pathways displayed differential gene expression under 6-BA treatment. A total of 283 transcription factors were categorized into 16 families, suggesting that CKs could enhance the growth and metabolism of industrial hemp. This study lays the groundwork for further exploring the molecular mechanisms of the CTK effect on industrial hemp. [ABSTRACT FROM AUTHOR]

Production quality plays a crucial role in individual well-being and national economic prosperity. Indian mustard (Brassica juncea L.), the third most vital oilseed crop globally and the second most cultivated in India after groundnut, faces challenges due to shrinking land availability and improper fertilizer use. These issues reduce mustard yields by limiting essential micronutrient uptake. This study investigated the impact of agrochemicals on mustard crops grown in reduced row spacing to boost yield. Mustard plants responded variably to boron, sulfur, and cytokinin foliar applications. The research assessed how these nutrients influence the crop’s growth, development, and yield under limited spacing conditions. Boron (0.5–1.5%) and sulfur (0.10–0.25%) were applied individually and in combination with cytokinin (0.003–0.0045%) as a foliar spray using a split-plot design. Morphological, physiological, biochemical, and yield-related parameters were carefully monitored. The application of these agrochemicals enhanced the mustard crop’s growth, physiology, and quality, improving production quality under limited space conditions. [ABSTRACT FROM AUTHOR]

Hyperhydricity is the most extensive physiological disorder during in vitro propagation. This disturbance can induce anatomical, morphological and physiological problems that cause serious damage. The factors that cause hyperhydricity are the composition of nutrient media and cultures conditions. To reduce the hyperhydricity of Pistacia khinjuk, ammonium nitrate (NH4NO3), calcium chloride (CaCl2·2H2O), cytokinins of meta-topolin (mT) and 6-benzylaminopurine (BAP) at different concentrations were investigated in Murashige and Skoog (MS) medium. The lowest percentage of hyperhydricity (34.30%) were obtained from the medium containing 1650 mg/L NH4NO3, 110 mg/L CaCl2·2H2O and1 mg/L mT; the highest percentage of hyperhydricity (68.42%) were obtained from the medium containing 206.25 mg/L NH4NO3, 440 mg/L CaCl2·2H2O and 0.5 mg/L BAP. The maximum average number of shoots per explant (2.45), average shoots length (18.47 mm) and proliferation rate (85%) were obtained from the medium containing 1650 mg/L NH4NO3, 110 mg/L CaCl2·2H2O of MS and 1 mg/L mT. In addition, when soluble protein (2.12 mg/g) and total chlorophyll a, b (0.96 mg/g) value of normal (non-hyperhydric) shoots were higher than hyperhydric shoots, carotenoid (11.75 µg /g) and water content (78.70%) value of normal shoots were lower than hyperhydric shoots. This study concludes that the hyperhydricity percentage of in vitro P. khinjuk shoots was reduced (12.8%) on modified MS medium with NH4NO3, CaCl2·2H2O and mT according to standard MS medium. [ABSTRACT FROM AUTHOR]

Common centaury (Centaurium eryhtraea Rafn) is a medicinal plant species with vigorous morphogenic potential in vitro. The process of spontaneous shoot regeneration in a solid root culture is characteristic for this plant species. In this context, the aim of this work was to investigate the dynamic changes of endogenous phytohormones and carbohydrates content in root explants at different time points (0, 2, 4, 7, 14, 21, 28, and 60 days) during spontaneous centaury morphogenesis in vitro. Detailed analysis of cytokinins (CKs) showed that trans -zeatin (tZ) was the major bioactive CK at all time points. The corresponding riboside, t Z9R, was also determined in the majority of the identified transport forms, at all time-points. Further analysis of endogenous auxin revealed a significant increase in endogenous indole-3-acetic acid (IAA) after 21 days, when a huge jump in the ratio of IAA/bioactive CKs was also observed. The maximum total soluble sugar content was measured after 14 days, while a significant decrease was determined after 21 days, when the first regenerated adventitious shoots appeared. This undoubtedly indicates an increased energy requirement prior to the actual regeneration of the shoots. The obtained results indicate that the period from day 14 to day 21 involves the most dramatic disturbances in endogenous bioactive CKs, IAA and carbohydrate balance, which are very important and valuable factors for the onset of shoot regeneration. [ABSTRACT FROM AUTHOR]

Summary: Plant root system is significantly influenced by high soil levels of ammonium nitrogen, leading to reduced root elongation and enhanced lateral root branching. In Arabidopsis, these processes have been reported to be mediated by phytohormones and their downstream signaling pathways, while the controlling mechanisms remain elusive in crops.Through a transcriptome analysis of roots subjected to high/low ammonium treatments, we identified a cytokinin oxidase/dehydrogenase encoding gene, CKX3, whose expression is induced by high ammonium. Knocking out CKX3 and its homologue CKX8 results in shorter seminal roots, fewer lateral roots, and reduced sensitivity to high ammonium.Endogenous cytokinin levels are elevated by high ammonium or in ckx3 mutants. Cytokinin application results in shorter seminal roots and fewer lateral roots in wild‐type, mimicking the root responses of ckx3 mutants to high ammonium. Furthermore, CKX3 is transcriptionally activated by type‐B RR25 and RR26, and ckx3 mutants have reduced auxin content and signaling in roots under low ammonium.This study identified RR25/26‐CKX3‐cytokinin as a signal module that mediates root responses to external ammonium by modulating of auxin signaling in the root meristem and lateral root primordium. This highlights the critical role of cytokinin metabolism in regulating rice root development in response to ammonium. [ABSTRACT FROM AUTHOR]

Summary: Hydrogen sulfide (H2S) is an endogenous gaseous signaling molecule, which has been shown to play an important role in plant growth and development by coupling with various phytohormones. However, the relationship between H2S and cytokinin (CTK) and the mechanisms by which H2S and CTK affect root growth remain poorly understood.Endogenous CTK was analyzed by UHPLC‐ESI‐MS/MS. Persulfidation of cytokinin oxidase/dehydrogenases (CKXs) was analyzed by mass spectrometry (MS). ckx2/CKX2wild‐type (WT), OE CKX2 and ckx2/CKX2Cys(C)62alanine(A) transgenic lines were isolated with the ckx2 background.H2S is linked to CTK content by CKX2, which regulates root system architecture (RSA). Persulfidation at cysteine (Cys)62 residue of CKX2 enhances CKX2 activity, resulting in reduced CTK content. We utilized 35S‐LCD/oasa1 transgenic lines to investigate the effect of endogenous H2S on RSA, indicating that H2S reduces the gravitropic set‐point angle (GSA), shortens root hairs, and increases the number of lateral roots (LRs). The persulfidation of CKX2Cys62 changes the elongation of cells on the upper and lower flanks of LR elongation zone, confirming that Cys62 of CKX2 is the specificity target of H2S to regulate RSA in vivo.In conclusion, this study demonstrated that H2S negatively regulates CTK content and affects RSA by persulfidation of CKX2Cys62 in Arabidopsis thaliana. [ABSTRACT FROM AUTHOR]

Jujube witches' broom, caused by phytoplasma, is a destructive disease of Chinese jujube. Studies have shown that zju‐miR156s play an important role in phytoplasma infection in jujube, but the regulatory mechanism between zju‐miR156c and witches' broom remains unexplored. In the current study, miRNA‐seq and gene expression analysis showed that zju‐miR156c was more highly induced in infected jujube plants than the other miRNAs and its target gene was ZjSPL3. In addition, the expression levels of thymidylate kinase gene (TMKJWB) and secreted jujube protein (SJP1JWB) in diseased materials were higher than those in healthy controls. The expression level of zju‐miR156c was significantly upregulated, while ZjSPL3 was sharply downregulated and the content of cytokinin (CTK) significantly increased. Overexpression of zju‐miR156c in Arabidopsis significantly reduced the expression of AtSPL10 (homologous gene of ZjSPL3) but increased the content of CTK, and the transgenic plants exhibited witches' broom symptoms. In addition, yeast two‐hybrid and co‐immunoprecipitation assays confirmed that SJP1JWB interacted with ZjERF18. Yeast one‐hybrid analysis showed that ZjERF18 could interact with the promoter of zju‐MIR156c. In conclusion, our results demonstrated a novel pathogenic module of ZjERF18‐zju‐miR156c‐ZjSPL3‐CTK has an important function in the formation of witches' broom caused by SJP1JWB. [ABSTRACT FROM AUTHOR]

Background: The plant hormone cytokinin is a conserved regulator of plant development. LONELY GUY (LOG) proteins are pivotal in cytokinin biosynthesis. However, their origin, evolutionary history, and enzymatic characteristics remain largely uncharacterized. Methods: To elucidate LOG family evolution history and protein motif composition, we conducted phylogenetic and motif analyses encompassing representative species across the whole green plant lineage. Catalytic activity and structure analysis were conducted to thoroughly characterize the LOG proteins. Results: Our phylogeny showed that LOG proteins could be divided into five groups and revealed three major duplication events giving rise to four distinct groups of vascular LOG proteins. LOG proteins share a conserved structure characterized by a canonical motif arrangement comprising motifs 1, 2, 3, 4, 5, 6, and 7. Two significant changes in LOG motif composition occurred during the transition to land plants: the emergence of motif 3 in charophyte LOG sequences and the subsequent acquisition of motif 8 at the C-terminus of LOG proteins. Enzymatic assays demonstrated that LOG proteins can be classified into two groups based on their enzyme activity. One group act as cytokinin riboside 5′-monophosphate phosphoribohydrolase and primarily convert iPRMP to iP, while the other group act as 5′-ribonucleotide phosphohydrolase, and preferentially produce iPR from the same substrates. TaLOG5-4A1, TaLOG5-4A2, TaLOG5-5B2, and TaLOG5-D1 shared conserved residues in the critical motif and were predicted to have similar protein structures, but displayed distinct enzymatic activities. Conclusions: Our findings provide a comprehensive overview of LOG protein phylogeny and lay a foundation for further investigations into their functional diversification. [ABSTRACT FROM AUTHOR]

Phytohormones are organic compounds produced in trace amounts within plants that regulate their physiological processes. Their physiological effects are highly complex and diverse. They influence processes ranging from cell division, elongation, and differentiation to plant germination and rooting. Therefore, phytohormones play a crucial regulatory role in plant growth and development. Recently, various studies have highlighted the role of PHs, such as auxin, cytokinin (CK), and abscisic acid (ABA), and newer classes of PHs, such as brassinosteroid (BR) and peptide hormone, in the plant responses toward environmental stresses. These hormones not only have distinct roles at different stages of plant growth but also interact to promote or inhibit each other, thus effectively regulating plant development. Roots are the primary organs for water and mineral absorption in plants. During seed germination, the radicle breaks through the seed coat and grows downward to form the primary root. This occurs because the root needs to quickly penetrate the soil to absorb water and nutrients, providing essential support for the plant's subsequent growth. Root development is a highly complex and precisely regulated process influenced by various signals. Changes in root architecture can affect the plant's ability to absorb nutrients and water, which in turn impacts crop yield. Thus, studying the regulation of root development is of great significance. Numerous studies have reported on the role of phytohormones, particularly auxins, in root regulation. This paper reviews recent studies on the regulation of root development by various phytohormones, both individually and in combination, providing a reference for researchers in this field and offering perspectives on future research directions for improving crop yields. [ABSTRACT FROM AUTHOR]

Plant somatic embryogenesis encompasses somatic cells switch into embryogenic cells that can later produce somatic embryos with the ability to produce plantlets. Previously, we defined in vitro culture settings for the somatic embryogenesis process of Coffea canephora that comprise adequate plantlets with auxin plus cytokinin followed by cut-leaf explant cultivation with cytokinin, producing embryos with the ability to regenerate plantlets. Here, we confirmed that cultivating cut-leaf explants with cytokinin is sufficient to promote somatic embryos proliferation and the high yield of somatic embryos in the protocol requires adequate plantlets with auxin plus cytokinin. Two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels reveal auxin-plus cytokinin-dependent regulated proteins in plantlets with up and down abundance. Chitinase A class III, proteins involved in the metabolism and folding of proteins, photosynthesis, antioxidant activity, and chromatin organization were identified. The RPN12 protein, which is a subunit of the proteasome 26S, has an abundance that is not associated with transcript changes, suggesting post-translational regulation. [ABSTRACT FROM AUTHOR]