Brassinosteroids Research Articles

Synergistic interaction between brassinosteroid and jasmonate pathways in rice response to cadmium toxicity

Brassinosteroids (BRs) and jasmonic acid (JA) are known to be involved in regulating plant responses to cadmium (Cd) stress. However, their specific roles and interaction in this process remain unclear. In this study, we discovered that exogenous BR alleviated Cd-mediated growth inhibition of rice seedlings. Enhanced Cd tolerance was also observed in m107, a BR-overproduction mutant. Phenotypic analysis of genetic materials involved in BR signaling confirmed the positive role of BR in regulating rice response to Cd toxicity. OsDLT, a key component in the BR signaling pathway, was found to be crucial for BR-mediated Cd tolerance. Further analysis demonstrated that activation of the BR pathway reduced the accumulation of Cd and reactive oxygen species (ROS) by modulating the expression of genes associated with Cd transport and ROS scavenging. Interestingly, transcriptome analysis indicated that the JA pathway was enriched in OsDLT-regulated differently expressed genes (DEGs). Gene expression and hormone assays showed that BR promoted the expression of JA pathway genes and JA levels in plants. Moreover, BR-induced tolerance was compromised in the JA signaling-deficient mutant osmyc2, suggesting that BR-mediated Cd resistance depends on the activation of the JA signaling pathway. Overall, our study revealed the synergistic interaction between BR and JA pathways in rice response to Cd stress, providing insights into the complex hormonal interplay in plant tolerance to heavy metals.

Phosphorylation of the transcription factor SlBIML1 by SlBIN2 kinases delays flowering in tomato.

Brassinosteroids (BRs) are well known for their important role in the regulation of plant growth and development. Plants with deficiency in BR signaling show delayed plant development and exhibit late flowering phenotypes. However, the precise mechanisms involved in this process require investigation. In this study, we cloned homologs of BRASSINOSTEROID INSENSITIVE 2 (SlBIN2), the GSK3-like protein kinase in tomato (Solanum lycopersicum). We characterized growth-related processes and phenotypic changes in the transgenic lines and found that SlBIN2s transgenic lines have delayed development and slow growing phenotypes. SlBIN2s work redundantly to negatively regulate BR signaling in tomato. Furthermore, the transcription factor SlBIN2.1-INTERACTING MYB-LIKE 1 (SlBIML1) was identified as a downstream substrate of SlBIN2s that SlBIN2s interact with and phosphorylate to synergistically regulate tomato developmental processes. Specifically, SlBIN2s modulated protein stability of SlBIML1 by phosphorylating multiple amino acid residues, including the sites Thr266 and Thr280. This study reveals a branch of the BR signaling pathway that regulates the vegetative growth phase and delays floral transition in tomato without the feedback affecting BR signaling. This information enriches our understanding of the downstream transduction pathway of BR signaling and provides potential targets for adjusting tomato flowering time.

BLA1 Affects Leaf Angles by Altering Brassinosteroid Biosynthesis in Rice (Oryza sativa L.).

Brassinosteroids (BRs) are crucial plant hormones influencing diverse developmental processes in rice. While several enzymes in BR biosynthesis have been identified, their regulatory mechanisms remain largely unknown. This study highlights a novel regulatory pathway wherein the CHD3 chromatin remodeler, BLA1, epigenetically modulates the expression of key BR biosynthesis genes, BRD1 and D2. Phenotypic analysis of bla1 mutants revealed significant alterations, such as increased leaf angles and longer mesocotyls, which were alleviated by BR synthesis inhibitors. Moreover, the bla1 mutants showed elevated BR levels that correlated with the significant upregulation of the expression levels of BRD1 and D2, particularly at the lamina joint sites. Mechanistically, the yeast one-hybrid and chromatin immunoprecipitation assays revealed specific binding of BLA1 to the promoter regions of BRD1 and D2, accompanied by a marked enrichment of the transcriptionally active histone modification, H3K4me3, on these loci in the bla1 mutant. Functional assessments of the brd1 and d2 mutants confirmed their reduced sensitivity to BR, further underscoring their critical regulatory roles in BR-mediated developmental processes. Our findings uncovered an epigenetic mechanism that governs BR biosynthesis and orchestrates the expression of BRD1 and D2 to modulate BR levels and influence rice growth and development.

Brassinolide and gibberellin promote grape fruit development and quality

Brassinosteroid (BR) and Gibberellins (GA) are important hormones that significantly influences grapeberry development and ripening. In the present study, grape clusters were soaked separately with EBR (Epi brassinolide), GA3, and EBR+GA3 during fruit development. Results showed that anthocyanin content, soluble solids, and titratable acid content were all enhanced by EBR treatment, however fruit weight, transverse and longitudinal longitude, and hardness were not significantly changed, furthermore, GA3 treatment increased the fruit weight, longitudinal and transverse longitude, and hardness, decreased titratable acid, and increased the solid acid ratio; The EBR+GA3 significantly improved grape fruit quality, increased fruit anthocyanin content, reduced titratable acid content, improved sugar-acid ratio, and significantly improved fruit weight, transverse and longitudinal longitude, and hardness. EBR and GA3 treatment increased the contents of alcohols, esters, ketones, terpenes, and phenols in aroma substances, and glucose and fructose. They also increased the sugar, aroma, and anthocyanin metabolism-related genes, while down-regulated the expression of acid-related genes. EBR also increased the GA metabolism associated genes, but GA3 decereaed BR metabolism assocated genes. BR and GA had a crosstalk of that VvGAI could interact with VvBZR1, VvGAI could inhibit the VvBZR1 binding to the VvGA20ox2 promoter that decreased the VvGA20ox2 gene expression, but EBR and GA3 could alleviate the inhibition. In conclusion, both BR and GA alone could improve fruit quality to some extent, and the combination of them can better integrate the advantages of single-use to improve the fruit quality and enhance the commerciality of the grape fruit.

The rice R2R3 MYB transcription factor FOUR LIPS connects brassinosteroid signaling to lignin deposition and leaf angle.

Leaf angle is an important agronomic trait for crop architecture and yield. In rice (Oryza sativa), the lamina joint is a unique structure connecting the leaf blade and sheath that determines leaf angle. Brassinosteroid (BR) signaling involving GLYCOGEN SYNTHASE KINASE-3 (GSK3)/SHAGGY-like kinases and BRASSINAZOLE-RESISTANT1 (BZR1) has a central role in regulating leaf angle in rice. In this study, we identified the atypical R2R3-MYB transcription factor FOUR LIPS (OsFLP), the rice homolog of Arabidopsis (Arabidopsis thaliana) AtFLP, as a participant in BR-regulated leaf angle formation. The spatiotemporal specificity of OsFLP expression in the lamina joint was closely associated with lignin deposition in vascular bundles and sclerenchyma cells. OsFLP mutation caused loose plant architecture with droopy flag leaves and hypersensitivity to BRs. OsBZR1 directly targeted OsFLP, and OsFLP transduced BR signals to lignin deposition in the lamina joint. Moreover, OsFLP promoted the transcription of the phenylalanine ammonia-lyase family genes OsPAL4 and OsPAL6. Intriguingly, OsFLP feedback regulated OsGSK1 transcription and OsBZR1 phosphorylation status. In addition, an Ala-to-Thr substitution within the OsFLP R3 helix-turn-helix domain, an equivalent mutation to that in Osflp-1, affected the DNA-binding ability and transcriptional activity of OsFLP. Our results reveal that OsFLP functions with OsGSK1 and OsBZR1 in BR signaling to maintain optimal leaf angle by modulating the lignin deposition in mechanical tissues of the lamina joint.

Fermentation broth of a novel endophytic fungus enhanced maize salt tolerance by regulating sugar metabolism and phytohormone biosynthesis or signaling

Soil salinization is a major environmental factor that severely affects global agriculture. Root endophytes can enter root cells, and offer various ecological benefits, such as promoting plant growth, improving soil conditions, and enhancing plant resistance. Su100 is a novel strain of endophytic fungus that was characterized from blueberry roots. In this study, we focused on evaluating the effects of Su100 secretion on maize growth. The results demonstrated that maize treated with Su100 fermentation broth (SFB) exhibited significantly stronger salt tolerance than the control. It is worth mentioning that the treated root system not only had an advantage in terms of biomass but also a change in root structure with a significant increase in lateral roots (LRs) compared to the control. Transcriptome analysis combined with hormone content measurements indicated that SFB upregulated the auxin signaling pathway, and also caused alterations in brassinosteroids (BR) and jasmonic acid (JA) biosynthesis and signaling pathways. Transcriptome analyses also indicated that SFB caused significant changes in the sugar metabolism of maize roots. The major changes included: enhancing the conversion and utilization of sucrose in roots; increasing carbon flow to uridine diphosphate glucose (UDPG), which acted as a precursor for producing more cell wall polysaccharides, mainly pectin and lignin; accelerating the tricarboxylic acid cycle, which were further supported by sugar content determinations. Taken together, our results indicated that the enhanced salt tolerance of maize treated with SFB was due to the modulation of sugar metabolism and phytohormone biosynthesis or signaling pathways. This study provided new insights into the mechanisms of action of endophytic fungi and highlighted the potential application of fungal preparations in agriculture.

Transcription factors BZR1 and PAP1 cooperate to promote anthocyanin biosynthesis in Arabidopsis shoots.

Anthocyanins play critical roles in protecting plant tissues against diverse stresses. The complicated regulatory networks induced by various environmental factors modulate the homeostatic level of anthocyanins. Here, we show that anthocyanin accumulation is induced by brassinosteroids (BRs) in Arabidopsis (Arabidopsis thaliana) shoots and shed light on the underlying regulatory mechanism. We observed that anthocyanin levels are altered considerably in BR-related mutants, and BRs induce anthocyanin accumulation by upregulating the expression of anthocyanin biosynthetic genes. Our genetic analysis indicated that BRASSINAZOLE RESISTANT 1 (BZR1) and PRODUCTION OF ANTHOCYANIN PIGMENT 1 (PAP1) are essential for BR-induced anthocyanin accumulation. The BR-responsive transcription factor BZR1 directly binds to the PAP1 promoter, regulating its expression. In addition, we found that intense anthocyanin accumulation caused by the pap1-D-dominant mutation is significantly reduced in BR mutants, implying that BR activity is required for PAP1 function after PAP1 transcription. Moreover, we demonstrated that BZR1 physically interacts with PAP1 to cooperatively regulate the expression of PAP1-target genes, such as TRANSPARENT TESTA 8, DIHYDROFLAVONOL 4-REDUCTASE, and LEUKOANTHOCYANIDIN DIOXYGENASE. Our findings indicate that BZR1 functions as an integral component of the PAP1-containing transcription factor complex, contributing to increased anthocyanin biosynthesis. Notably, we also show that functional interaction of BZR1 with PAP1 is required for anthocyanin accumulation induced by low nitrogen stress. Taken together, our results demonstrate that BR-regulated BZR1 promotes anthocyanin biosynthesis through cooperative interaction with PAP1 of the MBW complex.

The brassinosteroid receptor StBRI1 promotes tuber development by enhancing plasma membrane H+-ATPase activity in potato.

The brassinosteroid (BR) receptor BRASSINOSTEROID-INSENSITIVE 1 (BRI1) plays a critical role in plant growth and development. Although much is known about how BR signaling regulates growth and development in many crop species, the role of StBRI1 in regulating potato (Solanum tuberosum) tuber development is not well understood. To address this question, a series of comprehensive genetic and biochemical methods were applied in this investigation. It was determined that StBRI1 and Solanum tuberosum PLASMA MEMBRANE (PM) PROTON ATPASE2 (PHA2), a PM-localized proton ATPase, play important roles in potato tuber development. The individual overexpression of StBRI1 and PHA2 led to a 22% and 25% increase in tuber yield per plant, respectively. Consistent with the genetic evidence, in vivo interaction analysis using double transgenic lines and PM H+-ATPase activity assays indicated that StBRI1 interacts with the C-terminus of PHA2, which restrains the intramolecular interaction of the PHA2 C-terminus with the PHA2 central loop to attenuate autoinhibition of PM H+-ATPase activity, resulting in increased PHA2 activity. Furthermore, the extent of PM H+-ATPase autoinhibition involving phosphorylation-dependent mechanisms corresponds to phosphorylation of the penultimate Thr residue (Thr-951) in PHA2. These results suggest that StBRI1 phosphorylates PHA2 and enhances its activity, which subsequently promotes tuber development. Altogether, our results uncover a BR-StBRI1-PHA2 module that regulates tuber development and suggest a prospective strategy for improving tuberous crop growth and increasing yield via the cell surface-based BR signaling pathway.

Characterization of the Bax Inhibitor-1 Family in Cauliflower and Functional Analysis of BobBIL4.

The Bax inhibitor-1 (BI-1) gene family, which is important for plant growth, development, and stress tolerance, remains largely unexplored in cauliflower. In this study, we identified and characterized cauliflower BI-1 family genes. Based on aligned homologous sequences and collinearity with Arabidopsis genes, we identified nine cauliflower BI-1 genes, which encode proteins that varied in length, molecular weight, isoelectric point, and predicted subcellular localization, including the Golgi apparatus, plasma membrane, and various compartments within the chloroplast. Phylogenetic analyses detected evolutionary conservation and divergence among these genes. Ten structural motifs were identified, with Motif 5 found to be crucial for inhibiting apoptosis. According to the cis-regulatory elements in their promoters, these genes likely influence hormone signaling and stress responses. Expression profiles among tissues highlighted the functional diversity of these genes, with particularly high expression levels observed in the silique and root. Focusing on BobBIL4, we investigated its role in brassinosteroid (BR)-mediated root development and salt stress tolerance. BobBIL4 expression levels increased in response to BR and salt treatments. The functional characterization of this gene in Arabidopsis revealed that it enhances root growth and salinity tolerance. These findings provide insights into BI-1 gene functions in cauliflower while also highlighting the potential utility of BobBIL4 for improving crop stress resistance.

Understanding the amylose biosynthesis and regulation mechanisms in Tartary buckwheat by the endosperm transcriptome

Starch serves as a crucial energy source for both plants and humans, predominantly synthesized and stored in endosperms, tubers, rhizomes, and cotyledons. Given the significant role of amylose in determining the quality of starchy crops, optimizing its content has become a key objective in current crop breeding efforts. Tartary buckwheat, a dicotyledonous plant, notably accumulates high levels of amylose in its endosperm, surpassing common cereals like rice and maize. However, the mechanisms underlying amylose accumulation, distribution, and regulation in Tartary buckwheat remain unclear. Here, amylose content was determined across various tissues and organs of Tartary buckwheat, identifying with the endosperm as the primary site for its biosynthesis and accumulation. RNA sequencing analysis of endosperms from different developmental stages identified 35 genes potentially involved in starch biosynthesis, with 13 genes showing high endosperm-specific expression, suggesting crucial roles in starch biosynthesis. Additionally, the transcription factor FtNF-YB2, which was specifically highly expressed in the endosperm, was discovered to enhance amylose synthesis. Moreover, promoters with potential endosperm-specific activity were identified, advancing our understanding of amylose regulation. Additionally, this study also demonstrates that brassinosteroids (BR) positively influence amylose biosynthesis in Tartary buckwheat endosperm. These findings provide essential insights into the mechanisms of understanding amylose biosynthesis, accumulation and regulation in Tartary buckwheat, offering significant implications for future breeding strategies.

WITHDRAWN: Grape defense against gray mold involves VvBZR1-mediated autophagy

Brassinosteroids (BRs) are a class of polyhydroxylated steroidal phytohormones that effectively affect the disease resistance in grape. However, the molecular mechanism of BR signaling networks responsible for activation of host defense against gray mold infection remained to be elucidated. The induced resistance mechanism of eBR treatment on table grapes (Vitis vinifera L. cv. Thompson Seedless) was conducted by an artificial inoculation trial. Grape berries were soaked in 0.5 mg L-1 24-epibrassinolide solution, and Botrytis cinerea suspension was injected after 6 hours. We reported a novel defense mechanism that BR-regulated autophagy in grape berry against B. cinerea. Exogenous application of 24-epibrassinolide (eBR) enhanced the grape disease resistance. The eBR-treated berries activated an oxidation-reduction (redox), polyamines metabolism, and autophagy during Botrytis infection. Transcript of BR signaling pathway genes were up-regulated within 12 h. In addition, transcriptome analysis in EBR-treated grapes infected with gray mold showed that the differentially expressed genes (DEGs) were enriched in the metabolic pathway of BR signaling pathway and autophagy. Meanwhile, the endogenous BR, SA and JA accumulated transiently. Overexpressing and silencing VvBZR1 in grape significantly affected oxidation, autophagy, and defense response. DNA affinity purification sequencing (Dap-seq), Yeast one-hybrid assay (Y1H) and dual luciferase assays (LUC) verified VvBZR1 transcriptionally regulated the autophagy related gene VvATG18a. Overexpressing VvATG18a improved the resistance of grapes to gray mold. Overall, this study sheds light on the immune mechanisms underlying the involvement of the BR signal transduction pathway in grape innate immunity, highlighting the pivotal role of VvBZR1-mediated autophagy in enhancing disease resistance.

Brassinosteroid improves resistance to phosphorus deficiency stress through regulating nutrient balance and reactive oxygen species scavenging in potato

Brassinosteroid (BR) plays a crucial role in plant growth, development and response to abiotic stress. However, the mechanism by which BR regulates the response of potato plants to phosphorus deficiency stress is still largely unknown. In this work, the effects of BR on the growth of potato plants under phosphorus deficient condition were investigated. Exogenous BR application mitigated the growth inhibition caused by phosphorus deficiency stress. Transcriptomic analyses revealed that BR application altered the expression of genes involved in mitogen-activated protein kinase (MAPK) signaling pathway, plant hormone signal transduction, and nitrogen and phosphorus metabolisms under phosphorus deficient condition. Further gene ontology (GO) analysis indicated a significant enrichment of genes associated with reactive oxygen species scavenging process. Ectopic expression of potato brassinosteroid synthesis gene StCYP85A1 in Arabidopsis improved the resistance of transgenic plants to phosphorus deficiency stress, as indicated by the increased germination greening ratio and root growth. Quantitative real time PCR and antioxidant enzyme activity analysis revealed that ectopic expression of StCYP85A1 altered the expression of genes related to nitrogen and phosphorus metabolism, and promoted antioxidant enzyme activity in transgenic plants. These findings indicated that BR improved the tolerance of potato plants to phosphorus deficiency stress by regulating nutrient homeostasis and reactive oxygen species scavenging.

SlCPK27 cross-links SlHY5 and SlPIF4 in brassinosteroid-dependent photo- and thermo-morphogenesis in tomato.

ELONGATED HYPOCOTOYL5 (HY5) and PHYTOCHROME INTERACTING FACTORs (PIFs) are two types of important light-related regulators of plant growth, however, their interplay remains elusive. Here, we report that the activated tomato (Solanum lycopersicum) HY5 (SlHY5) triggers the transcription of a Calcium-dependent Protein Kinase SlCPK27. SlCPK27 interacts with and phosphorylates SlPIF4 at Ser-252 and Ser-308 phosphosites to promote its degradation. SlPIF4 promotes hypocotyl elongation mainly by activating the transcription of SlDWF, a key gene in brassinosteroid (BR) biosynthesis. Such a SlHY5-SlCPK27-SlPIF4-BR cascade not only plays a crucial role in photomorphogenesis but also regulates thermomorphogenesis. Our results uncover a previously unidentified mechanism that integrates Ca2+ signaling with the light signaling pathways to regulate plant growth by modulating BR biosynthesis in response to changes in ambient light and temperature.

Molecular Insights into the Role of Sterols in Microtuber Development of Potato Solanum tuberosum L.

Potato tubers are reproductive and storage organs, enabling their survival. Unraveling the molecular mechanisms that regulate tuberization is crucial for understanding how potatorespond to environmental stress situations and for potato breeding. Previously, we did a transcriptomic analysis of potato microtuberization without light. This showed that important cellular processes like ribosomal proteins, cell cycle, carbon metabolism, oxidative stress, fatty acids, and phytosterols (PS) biosynthesis were closely connected in a protein-protein interaction (PPI) network. Research on PS function during potato tuberization has been scarce. PS plays a critical role in regulating membrane permeability and fluidity, and they are biosynthetic precursors of brassinosteroids (BRs) in plants, which are critical in regulating gene expression, cell division, differentiation, and reproductive biology. Within a PPI network, we found a module of 15 genes involved in the PS biosynthetic process. Darkness, as expected, activated the mevalonate (MVA) pathway. There was a tight interaction between three coding gene products for HMGR3, MVD2, and FPS1, and the gene products that synthetize PS, including CAS1, SMO1, BETAHSD, CPI1, CYP51, FACKEL, HYDRA1, SMT2, SMO2, STE1, and SSR1. Quantitative real-time polymerase chain reaction (qRT-PCR) confirmed the expression analysis of ten specific genes involved in the biosynthesis of PS. This manuscript discusses the potential role of genes involved in PS biosynthesis during microtuber development.

Ectopic Expression of AetPGL from Aegilops tauschii Enhances Cadmium Tolerance and Accumulation Capacity in Arabidopsis thaliana.

Cadmium (Cd) is a toxic heavy metal that accumulates in plants, negatively affecting their physiological processes, growth, and development, and poses a threat to human health through the food chain. 6-phosphogluconolactonase (PGL) is a key enzyme in the Oxidative Pentose Phosphate Pathway(OPPP) in plant cells, essential for cellular metabolism. The OPPP pathway provides energy and raw materials for organisms and is involved in antioxidant reactions, lipid metabolism, and DNA synthesis. This study describes the Cd responsive gene AetPGL from Aegilops tauschii. Overexpression of AetPGL under Cd stress increased main root length and germination rate in Arabidopsis. Transgenic lines showed higher antioxidant enzyme activities and lower malondialdehyde (MDA) content compared to the wild type. The transgenic Arabidopsis accumulated more Cd in the aboveground part but not in the underground part. Expression levels of AtHMA3, AtNRAMP5, and AtZIP1 in the roots of transgenic plants increased under Cd stress, suggesting AetPGL may enhance Cd transport from root to shoot. Transcriptome analysis revealed enrichment of differentially expressed genes (DEGs) in the plant hormone signal transduction pathway in AetPGL-overexpressing plants. Brassinosteroids (BR), Gibbenellin acid (GA), and Jasmonic acid (JA) contents significantly increased after Cd treatment. These results indicate that AetPGL may enhance Arabidopsis' tolerance to Cd by modulating plant hormone content. In conclusion, AetPGL plays a critical role in improving cadmium tolerance and accumulation and mitigating oxidative stress by regulating plant hormones, providing insights into the molecular mechanisms of plant Cd tolerance.

GhEXL3 participates in brassinosteroids regulation of fiber elongation in Gossypium hirsutum.

Cotton fiber (Gossypium hirsutum) serves as an ideal model for investigating the molecular mechanisms of plant cell elongation at the single-cell level. Brassinosteroids (BRs) play a crucial role in regulating plant growth and development. However, the mechanism by which BR influences cotton fiber elongation remains incompletely understood. In this study, we identified EXORDIUM-like (GhEXL3) through transcriptome analysis of fibers from BR-deficient cotton mutant pagoda 1 (pag1) and BRI1-EMS-SUPPRESSOR 1 (GhBES1.4, encoding a central transcription factor of BR signaling) overexpression cotton lines. Knockout of GhEXL3 using CRISPR/Cas9 was found to impede cotton fiber elongation, while its overexpression promoted fiber elongation, suggesting a positive regulatory function for GhEXL3 in fiber elongation. Furthermore, in vitro ovule culture experiments revealed that the overexpression of GhEXL3 partially counteracted the inhibitory effects of brassinazole (BRZ) on cotton fiber elongation, providing additional evidence of GhEXL3 involvement in BR signaling pathways. Moreover, our findings demonstrate that GhBES1.4 directly binds to the E-box (CACGTG) motif in the GhEXL3 promoter region and enhances its transcription. RNA-seq analysis revealed that overexpression of GhEXL3 upregulated the expression of EXPs, XTHs, and other genes associated with fiber cell elongation. Overall, our study contributes to understanding the mechanism by which BR regulates the elongation of cotton fibers through the direct modulation of GhEXL3 expression by GhBES1.4.

24-epibrassinolide enhances drought tolerance in grapevine (Vitis vinifera L.) by regulating carbon and nitrogen metabolism.

Exogenous application of 24-epibrassinolide can alleviate oxidative damage, improve photosynthetic capacity, and regulate carbon and nitrogen assimilation, thus improving the tolerance of grapevine (Vitis vinifera L.) to drought stress. Brassinosteroids (BRs) are a group of plant steroid hormones in plants and are involved in regulating plant tolerance to drought stress. This study aimed to investigate the regulation effects of BRs on the carbon and nitrogen metabolism in grapevine under drought stress. The results indicated that drought stress led to the accumulation of superoxide radicals and hydrogen peroxide and an increase in lipid peroxidation. A reduction in oxidative damage was observed in EBR-pretreated plants, which was probably due to the improved antioxidant concentration. Moreover, exogenous EBR improved the photosynthetic capacity and sucrose phosphate synthase activity, and decreased the sucrose synthase, acid invertase, and neutral invertase, resulting in improved sucrose (190%) and starch (17%) concentrations. Furthermore, EBR pretreatment strengthened nitrate reduction and ammonium assimilation. A 57% increase in nitrate reductase activity and a 13% increase in glutamine synthetase activity were observed in EBR pretreated grapevines. Meanwhile, EBR pretreated plants accumulated a greater amount of proline, which contributed to osmotic adjustment and ROS scavenging. In summary, exogenous EBR enhanced drought tolerance in grapevines by alleviating oxidative damage and regulating carbon and nitrogen metabolism.

RACK1 links phyB and BES1 to coordinate brassinosteroid-dependent root meristem development.

Light and brassinosteroids (BR) are indispensable for plant growth and control cell division in the apical meristem. However, how external light signals cooperate with internal brassinosteroids to program root meristem development remains elusive. We reveal that the photoreceptor phytochrome B (phyB) guides the scaffold protein RACK1 to coordinate BR signaling for maintaining root meristematic activity. phyB and RACK1 promote early root meristem development. Mechanistically, RACK1 could reinforce the phyB-SPA1 association by interacting with both phyB and SPA1, which indirectly affects COP1-dependent RACK1 degradation, resulting in the accumulation of RACK1 in roots. Subsequently, RACK1 interacts with BES1 to repress its DNA-binding activity toward the target gene CYCD3;1, leading to the release of BES1-mediated inhibition of CYCD3;1 transcription, and hence the promotion of root meristem development. Our study provides mechanistic insights into the regulation of root meristem development by combination of light and phytohormones signals through the photoreceptors and scaffold proteins.

The Role of Brassinosteroids in Plant Cold Stress Response.

Temperature affects plant growth and geographical distribution. Cold stress occurs when temperatures fall below the physiologically optimal range for plants, causing permanent and irreversible damage to plant growth, development, and production. Brassinosteroids (BRs) are steroid hormones that play an important role in plant growth and various stress responses. Recent studies have shown that low temperatures affect BR biosynthesis in many plant species and that BR signaling is involved in the regulation of plant tolerance to low temperatures, both in the CBF-dependent and CBF-independent pathways. These two regulatory pathways correspond to transient and acclimation responses of low temperature, respectively. The crosstalk between BRs and other hormones is a significant factor in low-temperature tolerance. We provide an overview of recent developments in our knowledge of BRs' function in plant responses to cold stress and how they interact with other plant hormones in this review.

The cap-binding complex modulates ABA-responsive transcript splicing during germination in barley (Hordeum vulgare)

To decipher the molecular bases governing seed germination, this study presents the pivotal role of the cap-binding complex (CBC), comprising CBP20 and CBP80, in modulating the inhibitory effects of abscisic acid (ABA) in barley. Using both single and double barley mutants in genes encoding the CBC, we revealed that the double mutant hvcbp20.ab/hvcbp80.b displays ABA insensitivity, in stark contrast to the hypersensitivity observed in single mutants during germination. Our comprehensive transcriptome and metabolome analysis not only identified significant alterations in gene expression and splicing patterns but also underscored the regulatory nexus among CBC, ABA, and brassinosteroid (BR) signaling pathways.