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Brassinosteroids (BRs), one of the major classes of phytohormones are essential for various processes of plant growth, development, and adaptations to biotic and abiotic stresses. In Arabidopsis, AtCYP90D1 acts as a bifunctional cytochrome P450 monooxygenase, catalyzing C-23 hydroxylation in the brassinolide biosynthetic pathway. The present study reports the functional characterizations of PtoCYP90D1, one of the AtCYP90D1 homologous genes from Populus tomentosa. The qRT-PCR analysis showed that PtoCYP90D1 was highly expressed in roots and old leaves. Overexpression of PtoCYP90D1 (PtoCYP90D1-OE) in poplar promoted growth and biomass yield, as well as increased xylem area and cell layers. Transgenic plants exhibited a significant increase in plant height and stem diameter as compared to the wild type. In contrast, the CRISPR/Cas9-generated mutation of PtoCYP90D1 (PtoCYP90D1-KO) resulted in significantly decreased biomass production in transgenic plants. Further studies revealed that cell wall components increased significantly in PtoCYP90D1-OE lines but not in PtoCYP90D1-KO lines, as compared to wild-type plants. Overall, the findings indicate a positive role of PtoCYP90D1 in improving growth rate and elevating biomass production in poplar, which will have positive implications for its versatile industrial or agricultural applications. [ABSTRACT FROM AUTHOR]

Arsenic, a toxic contaminant found in agricultural fields, is known to affect crop yield negatively and is taken up by plants via the phosphate transport pathway, where accumulation reduces root shoot biomass and yield. Phytohormones are indispensable in promoting plant acclimatization to ever-changing environments by transducing environmental signals to various developmental, physiochemical, and stress responses. In the present study, using an in vitro germination model, we aim to understand the ameliorative role of 24-epibrassinolide, a synthetic brassinosteroid, in mitigating arsenate stress in rice seedlings. Further, a qRT-PCR analysis was performed to study the differential expression of genes involved in cell division, cell elongation, and those related to the biosynthesis of cell wall components. The cell wall architecture was also analyzed using scanning electron microscopy. Our study reports reversal of the toxicity symptoms caused by arsenate in the presence of 24-epibrassinolide, with a nearly 50% increase in root length and around 40% enhancement in shoot length, weight, and germination rate. Further, the expression of BR-responsive transcription factors, namely, OsBZR1, OsERF115, and OsMYB56, and their downstream targets involved in cell division and elongation at the quiescent center were significantly upregulated. 24-EBL application also increased the transcript level of key genes involved in cellulose biosynthesis, i.e., OsCesA3 and OsCesA6. In contrast, a significant decline in mRNA expression of OsPME11 and OsEXLA3 was observed with increased compactness in the arrangement of cellulose indicating restoration of cell wall architecture during arsenate stress alleviation. [ABSTRACT FROM AUTHOR]

Chlorophyll (Chl) is essential for plants to carry out photosynthesis, growth and development processes. Growth‐regulating factors (GRFs) play a vital role in regulating Chl degradation in plants. However, the molecular mechanism by which GRF5 regulates Chl degradation in poplar remains unknown. Here we found that overexpression of PpnGRF5‐1 increased Chl content in leaves and promoted chloroplast development in poplar. Overexpression of PpnGRF5‐1 in poplar delayed Chl degradation induced by external factors, such as hormones, darkness and salt stress. PpnGRF5‐1 responded to brassinosteroid (BR) signalling during BR‐induced Chl degradation and reduced the expression levels of Chl degradation and senescence‐related genes. PpnGRF5‐1 inhibited the expression of Chl b reductases PagNYC1 and PagNOL. PpnGRF5‐1 could interact with PagBZR1 in the nucleus. PagBZR1 also inhibited the expression of PagNYC1. In addition, we found that the protein–protein interaction between PagBZR1 and PpnGRF5‐1 enhanced the inhibitory effect of PpnGRF5‐1 on the Chl b reductases PagNYC1 and PagNOL. BZR1 and GRF5‐1 were upregulated, and NOL and NYC1 were downregulated in triploid poplars compared to diploids. This study revealed a new mechanism by which PpnGRF5‐1 regulates Chl degradation in poplars and lays the foundation for comprehensively analysing the molecular mechanism of Chl metabolism in triploid poplars. Summary statement: PpnGRF5‐1 could interact with PagBZR1 in the nucleus and bind to the promoter of the Chl b reductases PagNYC1 and PagNOL to regulate Chl degradation in poplar. [ABSTRACT FROM AUTHOR]

Helical growth of the root tip (circumnutation) that permits surface exploration facilitates root penetration into soil. Here, we reveal that rice actin-binding protein RMD aids in root circumnutation, manifested by wavy roots as well as compromised ability to efficiently explore and avoid obstacles in rmd mutants. We demonstrate that root circumnutation defects in rmd depend on brassinosteroid (BR) signaling, which is elevated in mutant roots. Suppressing BR signaling via pharmacological (BR inhibitor) or genetic (knockout of BR biosynthetic or signaling components) manipulation rescues root defects in rmd. We further reveal that mutations in MAPK6 suppress BR signaling and restore normal root circumnutation in rmd, which may be mediated by the interaction between MAPK6, MAPKK4 and BR signaling factor BIM2. Our study thus demonstrates that RMD and MAPK6 control root circumnutation by modulating BR signaling to facilitate early root growth. [ABSTRACT FROM AUTHOR]

Fruit color is a key feature of fruit quality, primarily influenced by anthocyanin or carotenoid accumulation or chlorophyll degradation. Adapting the pigment content is crucial to improve the fruit's nutritional and commercial value. Genetic factors along with other environmental components (i.e., light, temperature, nutrition, etc.) regulate fruit coloration. The fruit coloration process is influenced by plant hormones, which also play a vital role in various physiological and biochemical metabolic processes. Additionally, phytohormones play a role in the regulation of a highly conserved transcription factor complex, called MBW (MYB-bHLH-WD40). The MBW complex, which consists of myeloblastosis (MYB), basic helix–loop–helix (bHLH), and WD40 repeat (WDR) proteins, coordinates the expression of downstream structural genes associated with anthocyanin formation. In fruit production, the application of plant hormones may be important for promoting coloration. However, concerns such as improper concentration or application time must be addressed. This article explores the molecular processes underlying pigment formation and how they are influenced by various plant hormones. The ABA, jasmonate, and brassinosteroid increase anthocyanin and carotenoid formation, but ethylene, auxin, cytokinin, and gibberellin have positive as well as negative effects on anthocyanin formation. This article establishes the necessary groundwork for future studies into the molecular mechanisms of plant hormones regulating fruit color, ultimately aiding in their effective and scientific application towards fruit coloration.Key message: In this article, we have discussed the underlying molecular mechanism of hormonal regulation of fruit color in fruit-bearing plant species. The process of regulating fruit color is influenced by plant hormones which have a significant role in the physiological and biochemical metabolic processes and the control of gene expression and MBW complex activity. [ABSTRACT FROM AUTHOR]

Intercellular communication in plants, as in other multicellular organisms, allows cells in tissues to coordinate their responses for development and in response to environmental stimuli. Much of this communication is facilitated by plasmodesmata (PD), consisting of membranes and cytoplasm, that connect adjacent cells to each other. PD have long been viewed as passive conduits for the movement of a variety of metabolites and molecular cargoes, but this perception has been changing over the last two decades or so. Research from the last few years has revealed the importance of PD as signaling hubs and as crucial players in hormone signaling. The adoption of advanced biochemical approaches, molecular tools, and high-resolution imaging modalities has led to several recent breakthroughs in our understanding of the roles of PD, revealing the structural and regulatory complexity of these 'protoplasmic connecting threads'. We highlight several of these findings that we think well illustrate the current understanding of PD as functioning at the nexus of plant physiology, development, and acclimation to the environment. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract Brassinosteroids (BRs), one of the major classes of phytohormones are essential for various processes of plant growth, development, and adaptations to biotic and abiotic stresses. In Arabidopsis, AtCYP90D1 acts as a bifunctional cytochrome P450 monooxygenase, catalyzing C-23 hydroxylation in the brassinolide biosynthetic pathway. The present study reports the functional characterizations of PtoCYP90D1, one of the AtCYP90D1 homologous genes from Populus tomentosa. The qRT-PCR analysis showed that PtoCYP90D1 was highly expressed in roots and old leaves. Overexpression of PtoCYP90D1 (PtoCYP90D1-OE) in poplar promoted growth and biomass yield, as well as increased xylem area and cell layers. Transgenic plants exhibited a significant increase in plant height and stem diameter as compared to the wild type. In contrast, the CRISPR/Cas9-generated mutation of PtoCYP90D1 (PtoCYP90D1-KO) resulted in significantly decreased biomass production in transgenic plants. Further studies revealed that cell wall components increased significantly in PtoCYP90D1-OE lines but not in PtoCYP90D1-KO lines, as compared to wild-type plants. Overall, the findings indicate a positive role of PtoCYP90D1 in improving growth rate and elevating biomass production in poplar, which will have positive implications for its versatile industrial or agricultural applications.

The rapid elongation of rice (Oryza sativa) coleoptile is pivotal for the plant plumule to evade hypoxia stress induced by submergence, a condition often arising from overirrigation, ponding, rainstorms, or flooding. While brassinosteroids (BRs) are recognized for their diverse roles in plant growth and development, their influence on coleoptile elongation under hypoxic conditions remains largely unexplored. In this study, we demonstrate the significant requirement of BRs for coleoptile elongation in deep water. During coleoptile development, Glycogen Synthase Kinase3-Like Kinase2 (GSK2), the central inhibitor of BR signaling in rice, undergoes substantial suppression in deep water but induction in air. In contrast, the dephosphorylated form of BRASSINAZOLE RESISTANT1 (OsBZR1), representing the active form of the key BR signaling transcription factor, is induced in water but suppressed in air. Remarkably, the knockout of GSK3-like kinase genes significantly enhances coleoptile elongation in deep water, strongly indicating a vital contribution of BR response to hypoxia-stimulated coleoptile elongation. Transcriptome analysis uncovers both BR-associated and BR-independent hypoxia responses, implicating substance metabolism, redox reactions, abiotic stress responses, and crosstalk with other hormones in the regulation of BR-induced hypoxia responses. In summary, our findings suggest that rice plumules rapidly elongate coleoptiles through the activation of BR response in deep water, enabling them to escape from submergence-induced hypoxia stress.

Brassinosteroid (BR) is a hormone known for its crucial role in seed germination promotion. However, there is a limited understanding of potential application in tobacco seed. In this study, we investigated various active ingredients for seed coating to enhance tobacco seed germination. It revealed that seed coating with 0.0500 ppm BR and priming with 0.01 ppm BR significantly increased seed germination rates, especially in low-temperature conditions. In addition, the combined use BR with priming and seed coating exhibited a substantial improvement in seed germination rates and promoted seedling growth. Through transcriptional analysis, it found that BR treatment regulates the expression of genes associated with DNA synthesis, cell wall organization and glucan metabolic process involved in seed dormancy and seedling growth. Overall, these results provide valuable insights into the utilization of seed coating and priming techniques, particularly with the inclusion of BR, to enhance tobacco seed germination and facilitate seedling emergence. [ABSTRACT FROM AUTHOR]

Abstract Hydrogen sulfide (H2S) has emerged as a novel endogenous gas signaling molecule, joining the ranks of nitric oxide (NO) and carbon monoxide (CO). Recent research has highlighted its involvement in various physiological processes, such as promoting root organogenesis, regulating stomatal movement and photosynthesis, and enhancing plant growth, development, and stress resistance. Tobacco, a significant cash crop crucial for farmers’ economic income, relies heavily on root development to affect leaf growth, disease resistance, chemical composition, and yield. Despite its importance, there remains a scarcity of studies investigating the role of H2S in promoting tobacco growth. This study exposed tobacco seedlings to different concentrations of NaHS (an exogenous H2S donor) − 0, 200, 400, 600, and 800 mg/L. Results indicated a positive correlation between NaHS concentration and root length, wet weight, root activity, and antioxidant enzymatic activities (CAT, SOD, and POD) in tobacco roots. Transcriptomic and metabolomic analyses revealed that treatment with 600 mg/L NaHS significantly effected 162 key genes, 44 key enzymes, and two metabolic pathways (brassinosteroid synthesis and aspartate biosynthesis) in tobacco seedlings. The addition of exogenous NaHS not only promoted tobacco root development but also potentially reduced pesticide usage, contributing to a more sustainable ecological environment. Overall, this study sheds light on the primary metabolic pathways involved in tobacco root response to NaHS, offering new genetic insights for future investigations into plant root development.

Rice (Oryza sativa) plant architecture and grain shape, which determine grain quality and yield, are modulated by auxin and brassinosteroid via regulation of cell elongation and proliferation. We review the signal transduction of these hormones and the crosstalk between their signals on the regulation of rice plant architecture and grain shape. [ABSTRACT FROM AUTHOR]

Milk thistle (Silybum marianum (L.) Gaertn) is a globally and widely used medicinal plant that contains silymarin. This plant has antioxidant, antimicrobial, anticancer, hepatoprotective, cardiovascular‐protective, and neuroprotective effects. Plant quality, yield, and phytochemicals, especially silymarin content, change under various conditions like drought stress. Therefore, this research studied plant growth regulators (PGRs) like salicylic acid, spermidine, and brassinosteroid to increase plant tolerance to drought stress. Experimental treatments include different levels of irrigation (25%, 50%, 75%, and 90% field capacity), and foliar spraying including salicylic acid (75 and 150 mg/L), spermine (70 and 140 mg/L), and brassinosteroid (1 and 1.2 μM), separately, and water as a control and a secondary factor. The results revealed that the highest amount of leaf phenolic compounds was observed in the highest drought stress level (25%) and 75 mg/L salicylic acid application. Furthermore, brassinosteroid at different concentrations and salicylic acid (75 mg/L) increased leaf flavonoid content compared to other treatments. In 50% field capacity, foliar application of salicylic acid (150 mg/L) significantly increased seed yield by approximately 75% compared to control under the same stress level. Brassinosteroid application (1 μM) under 75% field capacity significantly increased the seed's taxifolin amount by 159%. Additionally, salicylic acid noticeably increased the silychristin concentration. The concentration of silydianin in the seed has also been increased under drought stress and foliar spraying with PGRs. Compared to the control, using spermidine below 75% field capacity caused an increase in its concentrations by over seven times. The highest silybin A amount was obtained in 50% field capacity and foliar150 mg/L salicylic acid. Taxifolin, silychristin, silydianin, silybinin B, iso‐silybinin A, and iso‐silybinin B compounds were identified in the seed extract. Generally, foliar spraying using plant growth regulators increased the number of silymarin compounds under drought stress conditions and field cultivation conditions. [ABSTRACT FROM AUTHOR]

The timing of the developmental transition from the vegetative to the reproductive stage is critical for angiosperms, and is fine-tuned by the integration of endogenous factors and external environmental cues to ensure successful reproduction. Plants have evolved sophisticated mechanisms to response to diverse environmental or stress signals, and these can be mediated by hormones to coordinate flowering time. Phytohormones such as gibberellin, auxin, cytokinin, jasmonate, abscisic acid, ethylene, and brassinosteroids and the cross-talk among them are critical for the precise regulation of flowering time. Recent studies of the model flowering plant Arabidopsis have revealed that diverse transcription factors and epigenetic regulators play key roles in relation to the phytohormones that regulate floral transition. This review aims to summarize our current knowledge of the genetic and epigenetic mechanisms that underlie the phytohormonal control of floral transition in Arabidopsis, offering insights into how these processes are regulated and their implications for plant biology. [ABSTRACT FROM AUTHOR]

SUMMARY: The interplay between microRNAs (miRNAs) and phytohormones allows plants to integrate multiple internal and external signals to optimize their survival of different environmental conditions. Here, we report that miR394 and its target gene LEAF CURLING RESPONSIVENESS (LCR), which are transcriptionally responsive to BR, participate in BR signaling to regulate hypocotyl elongation in Arabidopsis thaliana. Phenotypic analysis of various transgenic and mutant lines revealed that miR394 negatively regulates BR signaling during hypocotyl elongation, whereas LCR positively regulates this process. Genetically, miR394 functions upstream of BRASSINOSTEROID INSENSITIVE2 (BIN2), BRASSINAZOLEs RESISTANT1 (BZR1), and BRI1‐EMS‐SUPPRESSOR1 (BES1), but interacts with BRASSINOSTEROID INSENSITIVE1 (BRI1) and BRI1 SUPRESSOR PROTEIN (BSU1). RNA‐sequencing analysis suggested that miR394 inhibits BR signaling through BIN2, as miR394 regulates a significant number of genes in common with BIN2. Additionally, miR394 increases the accumulation of BIN2 but decreases the accumulation of BZR1 and BES1, which are phosphorylated by BIN2. MiR394 also represses the transcription of PACLOBUTRAZOL RESISTANCE1/5/6 and EXPANSIN8, key genes that regulate hypocotyl elongation and are targets of BZR1/BES1. These findings reveal a new role for a miRNA in BR signaling in Arabidopsis. Significance Statement: miR394 and its target gene LEAF CURLING RESPONSIVENESS are involved in BR signaling by affecting BRASSINOSTEROID INSENSITIVE2 accumulation. [ABSTRACT FROM AUTHOR]

Summary: Regulation of grain size is a crucial strategy for improving the crop yield and is also a fundamental aspect of developmental biology. However, the underlying molecular mechanisms governing grain development in wheat remain largely unknown. In this study, we identified a wheat atypical basic helix–loop–helix (bHLH) transcription factor, TabHLH489, which is tightly associated with grain length through genome‐wide association study and map‐based cloning. Knockout of TabHLH489 and its homologous genes resulted in increased grain length and weight, whereas the overexpression led to decreased grain length and weight. TaSnRK1α1, the α‐catalytic subunit of plant energy sensor SnRK1, interacted with and phosphorylated TabHLH489 to induce its degradation, thereby promoting wheat grain development. Sugar treatment induced TaSnRK1α1 protein accumulation while reducing TabHLH489 protein levels. Moreover, brassinosteroid (BR) promotes grain development by decreasing TabHLH489 expression through the transcription factor BRASSINAZOLE RESISTANT1 (BZR1). Importantly, natural variations in the promoter region of TabHLH489 affect the TaBZR1 binding ability, thereby influencing TabHLH489 expression. Taken together, our findings reveal that the TaSnRK1α1‐TabHLH489 regulatory module integrates BR and sugar signalling to regulate grain length, presenting potential targets for enhancing grain size in wheat. [ABSTRACT FROM AUTHOR]

Copyright of Harran Journal of Agricultural & Food Science is the property of Harran University, Faculty of Agriculture and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Ege Üniversitesi Ziraat Fakültesi Dergisi is the property of Ege Universitesi, Ziraat Fakultesi and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The awn is a bristle-like appendage that protrudes from the seed tip and plays a critical role in preventing feed damage and spreading habitats in many grass species, including rice. While all wild species in the Oryza genus have awns, this trait has been eliminated in domesticated species due to its obstructive nature to agricultural processes. To date, several genes involved in awn development have been identified in wild rice, Oryza rufipogon and Oryza barthii which are ancestral species of cultivated rice in Asia and Africa, respectively. However, the responsible genes for awn development have not been identified in other wild rice species even though multiple QTLs have been reported previously. In this study, we identified An7 gene responsible for awn development in two wild rice species, Oryza glumaepatula and Oryza meridionalis. An7 encodes a cytochrome P450 enzyme and is homologous to D2/CYP90D2, a known brassinosteroid biosynthesis enzyme in rice. The identification of An7 provides insight into a distinct molecular mechanism underlying awn development that occurs in geographically separated environments. [ABSTRACT FROM AUTHOR]

Xinjiang cotton is characterized by high-density planting, which easily leads to competition between the source and sink, the shading of leaves and reproductive organs, and yield reduction. Balancing the relationship between source and sink can promote high and stable cotton yield. In this study, field experiments were conducted by combining the exogenous application of brassinosteroid with a reduction in leaf source to study their effects on the physiological and yield attributes of cotton. The results indicate that brassinosteroid application increased the yield, with a maximum yield increase of 6.3%. The number of bolls per plant increased by 1.3 nos. The photosynthetic rate and dry matter accumulation were enhanced, and the proportion of reproductive organs in the dry matter increased by >4%. Under the reduced leaf source, brassinosteroid application increased the number of new leaves by 20%, delayed the shedding of reproductive organs by 5–10 days, and reduced the average shedding rate by 8.9%. Additionally, the number of bolls increased in the middle and upper parts and at the edge of the plant. The number of bolls increased by 19.4% on the 4th–8th fruiting branches and 60.7% at the edge. Under leaf reduction treatment, brassinosteroid application could generally increase yield. After brassinosteroid application and removing half the leaves of fruiting branches and all leaves of the vegetive branches, the yield was higher than that of the control. Thus, brassinosteroid application could improve the efficiency of the leaf source and promote dry matter accumulation in sinks. Moreover, it could optimize boll distribution and increase yield by reducing reproductive organ shedding. Under the high-density planting of cotton in Xinjiang, leaf source is a slight surplus, and a moderate reduction in plant density is conducive to increasing yield. [ABSTRACT FROM AUTHOR]

Members of the genus Klebsormidium are ubiquitously distributed over the Earth and are among the major biological soil crust (BSC) forming microalgae. Their representatives can be found in terrestrial, aquatic, polar, desert regions and have been investigated so far from various aspects. However, the available information about Klebsormidium isolates from lamp-flora is very limited. In our work, we examined a Klebsormidium strain isolated from a Hungarian cave. The temperature optimum of its photosynthetic performance was tested by oxygen yield measurements and pulse-amplitude-modulated fluorescence, which were completed by determination of specific growth rates at different temperatures, from 10 to 40 °C. In addition, we also evaluated the brassinosteroid (BR) content of these cultures. Our results indicated that the studied microalga is capable of growing from 10 to 40 °C, with a 20–25 °C temperature optimum; these findings were in accordance with the observed hormone levels. Regarding photosynthetic performance, the oxygen yield and chlorophyll fluorescence measurements showed maxima at 30–40 °C and 35–40 °C, respectively. Moreover, the examined Klebsormidium strain demonstrates traits associated with cave adaptation, i.e., by high light utilisation factor (α) and diminished light adaptation parameter (Ik) values. [ABSTRACT FROM AUTHOR]

ABSTRACT The 24-epibrassinolide (24-EpiBL), in association with the physiological conditioning of seeds, is recognized for providing several advantages in seeds, among which the most important one is the tolerance to abiotic stresses. Thus, the objective of this work was to evaluate the vigor of pepper seeds primed with 24-EpiBL and then subjected to salt stress. Three lots of pepper seeds of the cultivar Airetama Biquinho Amarela were used. The research was divided into three steps: the first for initial characterization of seed lots upon germination and vigor tests; the second for defining the water absorption process and drying of primed seeds; and the third for the priming of seeds with water (hydropriming) and 24-EpiBL (10-8 M), as well as priming with 24-EpiBL (10-8 M) of seeds subjected to the salt stress with the following osmotic potentials: 0.0, -0.2, and -0.4 MPa. A mitigation of deleterious effects of salt stress was found in seeds hydro-primed and primed with 24-EpiBL. The use of pepper seeds hydro-primed and primed with 24-EpiBL (10-8 M) is a viable alternative for decreasing injuries, morphological and biochemical changes, and growth and development limitations caused by salt stress.

The plant root absorbs water and nutrients, anchors the plant in the soil, and promotes plant development. Root is developed from root apical meristem (RAM), which is formed during embryo stage and is maintained by dividing stem cells. Plant hormones have a predominant role in RAM maintenance. This review evaluates the functional crosstalk among three major hormones (auxin, cytokinin, and brassinolide) in RAM development in Arabidopsis, integrating a variety of experimental data into a regulatory network and revealing multiple layers of complexity in the crosstalk among these three hormones. We also discuss possible directions for future research on the roles of hormones in regulating RAM development and maintenance.

Plants modify their root system architecture (RSA) in response to nitrogen (N) deficiency. The plant steroidal hormone, brassinosteroid (BR), plays important roles in root growth and development. This study demonstrates that optimal levels of exogenous BR impact significant increases in lateral root length and numbers in Arabidopsis seedlings under mild N-deficient conditions as compared to untreated seedlings. The impact of BR on RSA was stronger under mild N deficiency than under N-sufficient conditions. The BR effects on RSA were mimicked in dominant mutants of BZR1 and BES1 (bzr1-1D and bes1-D) transcription factors, while the RSA was highly reduced in the BR-insensitive mutant bri1-6, confirming that BR signaling is essential for the development of RSA under both N-sufficient and N-deficient conditions. Exogenous BR and constitutive activity of BZR1 and BES1 in dominant mutants led to enhanced root meristem, meristematic cell number, and cortical cell length. Under mild N deficiency, bzr1-1D displayed higher fresh and dry shoot weights, chlorophyll content, and N levels in the shoot, as compared to the wild type. These results indicate that BR modulates RSA under both N-sufficient and N-deficient conditions via the transcription factors BES1/BZR1 module and confers tolerance to N deficiency. [ABSTRACT FROM AUTHOR]

Mitochondrial protein homeostasis is crucially regulated by protein degradation processes involving both mitochondrial proteases and cytosolic autophagy. However, it remains unclear how plant cells regulate autophagy in the scenario of lacking a major mitochondrial Lon1 protease. In this study, we observed a notable downregulation of core autophagy proteins in Arabidopsis Lon1 knockout mutant lon1-1 and lon1-2, supporting the alterations in the relative proportions of mitochondrial and vacuolar proteins over total proteins in the plant cells. To delve deeper into understanding the roles of the mitochondrial protease Lon1 and autophagy in maintaining mitochondrial protein homeostasis and plant development, we generated the lon1-2atg5-1 double mutant by incorporating the loss-of-function mutation of the autophagy core protein ATG5, known as atg5-1. The double mutant exhibited a blend of phenotypes, characterized by short plants and early senescence, mirroring those observed in the individual single mutants. Accordingly, distinct transcriptome alterations were evident in each of the single mutants, while the double mutant displayed a unique amalgamation of transcriptional responses. Heightened severity, particularly evident in reduced seed numbers and abnormal embryo development, was observed in the double mutant. Notably, aberrations in protein storage vacuoles (PSVs) and oil bodies were evident in the single and double mutants. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses of genes concurrently downregulated in lon1-2, atg5-1, and lon1-2atg5-1 unveiled a significant suppression of genes associated with brassinosteroid (BR) biosynthesis and homeostasis. This downregulation likely contributes to the observed abnormalities in seed and embryo development in the mutants. [ABSTRACT FROM AUTHOR]

Key message: The study on the GmDWF1-deficient mutant dwf1 showed that GmDWF1 plays a crucial role in determining soybean plant height and yield by influencing the biosynthesis of brassinosteroids. Soybean has not adopted the Green Revolution, such as reduced height for increased planting density, which have proven beneficial for cereal crops. Our research identified the soybean genes GmDWF1a and GmDWF1b, homologous to Arabidopsis AtDWF1, and found that they are widely expressed, especially in leaves, and linked to the cellular transport system, predominantly within the endoplasmic reticulum and intracellular vesicles. These genes are essential for the synthesis of brassinosteroids (BR). Single mutants of GmDWF1a and GmDWF1b, as well as double mutants of both genes generated through CRISPR/Cas9 genome editing, exhibit a dwarf phenotype. The single-gene mutant exhibits moderate dwarfism, while the double mutant shows more pronounced dwarfism. Despite the reduced stature, all types of mutants preserve their node count. Notably, field tests have shown that the single GmDWF1a mutant produced significantly more pods than wild-type plants. Spraying exogenous brassinolide (BL) can compensate for the loss in plant height induced by the decrease in endogenous BRs. Comparing transcriptome analyses of the GmDWF1a mutant and wild-type plants revealed a significant impact on the expression of many genes that influence soybean growth. Identifying the GmDWF1a and GmDWF1b genes could aid in the development of compact, densely planted soybean varieties, potentially boosting productivity. [ABSTRACT FROM AUTHOR]

Rose black spot disease caused by Marssonina rosae is among the most destructive diseases that affects the outdoor cultivation and production of roses; however, the molecular mechanisms underlying the defensive response of roses to M. rosae have not been clarified. To investigate the diversity of response to M. rosae in resistant and susceptible rose varieties, we performed transcriptome and metabolome analyses of resistant (KT) and susceptible (FG) rose varieties and identified differentially expressed genes (DEGs) and differentially accumulated metabolites (DAMs) in response to M. rosae at different time points. In response to M. rosae, DEGs and DAMs were mainly upregulated compared to the control and transcription factors were concentrated in the WRKY and AP2/ERF families. Gene Ontology analysis showed that the DEGs of FG were mainly enriched in biological processes, such as the abscisic acid-activated signaling pathway, cell wall, and defense response, whereas the DEGs of KT were mainly enriched in Golgi-mediated vesicle transport processes. Kyoto Encyclopedia of Genes and Genomes analysis showed that the DEGs of both varieties were concentrated in plant-pathogen interactions, plant hormone signal transduction, and mitogen-activated protein kinase signaling pathways, with the greatest number of DEGs associated with brassinosteroid (BR) in the plant hormone signal transduction pathway. The reliability of the transcriptome results was verified by qRT-PCR. DAMs of KT were significantly enriched in the butanoate metabolism pathway, whereas DAMs of FG were significantly enriched in BR biosynthesis, glucosinolate biosynthesis, and tryptophan metabolism. Moreover, the DAMs in these pathways were significantly positively correlated with the DEGs. Disease symptoms were aggravated when FG leaves were inoculated with M. rosae after 24-epibrassinolide treatment, indicating that the response of FG to M. rosae involves the BR signaling pathway. Our results provide new insights into the molecular mechanisms underlying rose response to M. rosae and lay a theoretical foundation for formulating rose black spot prevention and control strategies and cultivating resistant varieties. [ABSTRACT FROM AUTHOR]

In Arabidopsis roots, the quiescent center (QC), a group of slowly dividing cells located at the center of the stem cell niche, functions as an organizing center to maintain the stemness of neighboring cells. Recent studies have shown that they also act as a reservoir for backup cells, which replenish DNA-damaged stem cells by activating cell division. The latter function is essential for maintaining stem cells under stressful conditions, thereby guaranteeing post-embryonic root development in fluctuating environments. In this study, we show that one of the brassinosteroid receptors in Arabidopsis, BRASSINOSTEROID INSENSITIVE1-LIKE3 (BRL3), plays a major role in activating QC division in response to DNA double-strand breaks. SUPPRESSOR OF GAMMA RESPONSE 1, a master transcription factor governing DNA damage response, directly induces BRL3. DNA damage-induced QC division was completely suppressed in brl3 mutants, whereas QC-specific overexpression of BRL3 activated QC division. Our data also showed that BRL3 is required to induce the AP2-type transcription factor ETHYLENE RESPONSE FACTOR 115, which triggers regenerative cell division. We propose that BRL3-dependent brassinosteroid signaling plays a unique role in activating QC division and replenishing dead stem cells, thereby enabling roots to restart growing after recovery from genotoxic stress. [ABSTRACT FROM AUTHOR]

Summary: Brassinosteroids (BRs) are plant hormones that are essential in plant growth and development. BRASSINOSTEROID‐INSENSITIVE 1 (BRI1) and BRI1 ASSOCIATED RECEPTOR KINASE 1 (BAK1), which are located on the plasma membrane, function as co‐receptors that accept and transmit BR signals.PROHIBITIN 3 (PHB3) was identified in both BRI1 and BAK1 complexes by affinity purification and LC‐MS/MS analysis. Biochemical data showed that BRI1/BAK1 interacted with PHB3 in vitro and in vivo.BRI1/BAK1 phosphorylated PHB3 in vitro. When the Thr‐80 amino acid in PHB3 was mutated to Ala, the mutant protein was not phosphorylated by BRI1 and the mutant protein interaction with BRI1 was abolished in the yeast two‐hybrid assay. BAK1 did not phosphorylate the mutant protein PHB3T54A. The loss‐of‐function phb3 mutant showed a weaker BR signal than the wild‐type. Genetic analyses revealed that PHB3 is a BRI1/BAK1 downstream substrate that participates in BR signalling. PHB3 has five homozygous in tomato, and we named the closest to AtPHB3 as SlPHB3.1. Biochemical data showed that SlBRI1/SlSERK3A/SlSERK3B interacted with SlPHB3.1 and SlPHB3.3. The CRISPR‐Cas9 method generated slphb3.1 mutant led to a BR signal stunted relatively in tomatoes.PHB3 is a new component of the BR signal pathway in both Arabidopsis and tomato. [ABSTRACT FROM AUTHOR]

Brassinosteroid (BR) has been shown to modulate plant tolerance to various stresses. S‐nitrosoglutathione reductase (GSNOR) is involved in the plant response to environment stress by fine‐turning the level of nitric oxide (NO). However, whether GSNOR is involved in BR‐regulated Na+/K+ homeostasis to improve the salt tolerance in halophyte is unknown. Here, we firstly reported that high salinity increases the expression of BR‐biosynthesis genes and the endogenous levels of BR in mangrove Kandelia obovata. Then, salt‐induced BR triggers the activities and gene expressions of GSNOR and antioxidant enzymes, thereafter decrease the levels of malondialdehyde, hydrogen peroxide. Subsequently, BR‐mediated GSNOR negatively regulates NO contributions to the reduction of reactive oxygen species generation and induction of the gene expression related to Na+ and K+ transport, leading to the decrease of Na+/K+ ratio in the roots of K. obovata. Finally, the applications of exogenous BR, NO scavenger, BR biosynthetic inhibitor and GSNOR inhibitor further confirm the function of BR. Taken together, our result provides insight into the mechanism of BR in the response of mangrove K. obovata to high salinity via GSNOR and NO signaling pathway by reducing oxidative damage and modulating Na+/K+ homeostasis. Summary Statement: Salinity increases brassinosteroid (BR)‐biosynthesis genes expression and endogenous BR in mangrove Kandelia obovata. BR enhances the activity and gene expression of S‐nitrosoglutathione reductase that negatively regulates nitric oxide signaling and reactive oxygen species level, while, BR regulates antioxidant enzymes and Na+/K+ homeostasis. [ABSTRACT FROM AUTHOR]

F-box proteins participate in the regulation of many processes, including cell division, development, and plant hormone responses. Brassinosteroids (BRs) regulate plant growth and development by activating core transcriptional and other multiple factors. In rice, OVATE family proteins (OFPs) participate in BR signalling and regulate grain size. Here we identified an F-box E3 ubiquitin ligase, FBX206, that acts as a negative factor in BR signalling and regulates grain size and yield in rice. Suppressed expression of FBX206 by RNAi leads to promoted plant growth and increased grain yield. Molecular analyses showed that the expression levels of BR biosynthetic genes were up-regulated, whereas those of BR catabolic genes were down-regulated in FBX206-RNAi plants, resulting in the accumulation of 28-homoBL, one of the bioactive BRs. FBX206 interacted with OsOFP8, a positive regulator in BR signalling, and OsOFP19, a negative regulator in BR signalling. SCFFBX206 mediated the degradation of OsOFP8 but suppressed OsOFP19 degradation. OsOFP8 interacted with OsOFP19, and the reciprocal regulation between OsOFP8 and OsOFP19 required the presence of FBX206. FBX206 itself was ubiquitinated and degraded, but interactions of OsOFP8 and OsOFP19 synergistically suppressed the degradation of FBX206. Genetic interactions indicated an additive effect between FBX206 and OsOFP8 and epistatic effects of OsOFP19 on FBX206 and OsOFP8. Our study reveals the regulatory networks of FBX206, OsOFP8, and OsOFP19 in BR signalling that regulate grain size and yield in rice. [ABSTRACT FROM AUTHOR]

BACKGROUND: Changes in apple fruit quality indices in response to foliar spray with 24‐epibrassinolide (EBL) at 0 and 1 μmol L−1 and methyl jasmonate (MeJA) at 0 and 0.5 μmol L−1, as well as the combination of these phytohormones, were investigated at harvest and during cold storage. RESULTS: Both phytohormones synergistically enhanced the fruit firmness, specific weight, size, fresh weight, water content, total antioxidant activity, total phenolics, ascorbic acid, total anthocyanins, total soluble solids/titratable acidity ratio and precocity. In addition, the fruit abscission pattern was changed in response to different treatments. Treated fruit exhibited lower weight loss and internal breakdown symptoms and higher total soluble solids index, firmness and phytochemicals during cold storage. A negative correlation was seen between fruit mass, firmness, specific weight, antioxidant activity, total phenolics and vitamin C content with internal breakdown occurrence and weight loss. CONCLUSION: Foliar spray with EBL and MeJA during the growth season is a good environmental friendly and safe method for enhancing the apple fruit different quality parameters, marketability and postharvest life. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

SUMMARY: Brassinazole Resistant 1 (BZR1) and bri1 EMS Suppressor 1 (BES1) are key transcription factors that mediate brassinosteroid (BR)‐responsive gene expression in Arabidopsis. The BZR1/BES1 family is composed of BZR1, BES1, and four BES1/BZR1 homologs (BEH1–BEH4). However, little is known about whether BEHs are regulated by BR signaling in the same way as BZR1 and BES1. We comparatively analyzed the functional characteristics of six BZR1/BES1 family members and their regulatory mechanisms in BR signaling using genetic and biochemical analyses. We also compared their subcellular localizations regulated by the phosphorylation status, interaction with GSK3‐like kinases, and heterodimeric combination. We found that all BZR1/BES1 family members restored the phenotypic defects of bri1‐5 by their overexpression. Unexpectedly, BEH2‐overexpressing plants showed the most distinct phenotype with enhanced BR responses. RNA‐Seq analysis indicated that overexpression of both BZR1 and BEH2 regulates BR‐responsive gene expression, but BEH2 has a much greater proportion of BR‐independent gene expression than BZR1. Unlike BZR1 and BES1, the BR‐regulated subcellular translocation of the four BEHs was not tightly correlated with their phosphorylation status. Notably, BEH1 and BEH2 are predominantly localized in the nucleus, which induces the nuclear accumulation of other BZR1/BES1 family proteins through heterodimerization. Altogether, our comparative analyses suggest that BEH1 and BEH2 play an important role in the functional interaction between BZR1/BES1 family transcription factors. Significance Statement: Our study is of significance as it thoroughly analyzed the functional characteristics of all six BZR1/BES1 family members and their regulatory mechanisms, which has not been attempted before. Our study expands the knowledge of the molecular mechanisms underlying the BR‐mediated transcriptional regulation network. [ABSTRACT FROM AUTHOR]

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Exogenous application of phytohormones is getting promising results in alleviating abiotic stresses, particularly heavy metal (HMs). Jasmonate (JA) and brassinosteroid (BR) have crosstalk in bamboo plants, reflecting a burgeoning area of investigation. Lead (Pb) is the most common pollutant in the environment, adversely affecting plants and human health. The current study focused on the foliar application of 10 µM JA and 10 µM BR in both single and combination forms on bamboo plants grown under Pb stress (0, 50, 100, 150 µM) with a completely randomized design by four replications. The study found that applying 10 µM JA and 10 µM BR significantly improves growth and tolerance by reducing oxidative stress, reactive oxygen species including hydrogen peroxide (H2O2, 32.91%), superoxide radicals (O2−•, 33.9%), methylglyoxal (MG, 19%), membrane lipoperoxidation (25.66%), and electrolyte leakage (41.5%) while increasing antioxidant (SOD (18%), POD (13%), CAT (20%), APX (12%), and GR (19%)), non-antioxidant (total phenolics (7%), flavonols (12.3%), and tocopherols (13.8%)), and glyoxylate activity (GLyI (13%), GLyII (19%)), proline content (19%), plant metal chelating capacity (17.3%), photosynthetic pigments (16%), plant growth (10%), and biomass (12%). We found that JA and BR, in concert, boost bamboo species' Pb tolerance by enhancing antioxidant and glyoxalase cycles, ion chelation, and reducing metal translocation and accumulation. This conclusively demonstrates that utilizing a BR–JA combination form at 10 µM dose may have the potential to yield optimal efficiency in mitigating oxidative stress in bamboo plants. [ABSTRACT FROM AUTHOR]

This article explores the role of brassinosteroids (BRs) in regulating bud outgrowth and crop architecture. Short stature crops developed during the green revolution disrupted the gibberellin (GA) pathway, leading to reduced height but increased tillering. BRs have emerged as an alternative dwarfing pathway that can decouple tillering from height. The article discusses how BRs integrate with the branching signaling network, particularly through the transcription factor TB1, and highlights the potential for genetic manipulation of BR biosynthesis or signaling components to modify shoot architecture. Further research is needed to understand the effects of BRs on other branching hormones and to uncover new targets for modifying crop architecture. [Extracted from the article]

Brassinosteroids (BR) signaling pathway is believed to be largely conserved among different species, although some components, steps, or events may differ between rice and Arabidopsis thaliana. BRs play essential roles in regulating both yield and stress-related traits, as well as in environmental adaptability, and thus hold promise for producing high-yielding and stable crops with less input. BR genes have been shown to be valuable for crop improvement employing various approaches. One prevalent method is to enhance the planting density of rice, maize, and wheat. Strategies such as exploring function-specific genes, identifying beneficial alleles, inducing favorable mutations, and optimizing the spatial hormone distribution can facilitate the utilization of BR genes towards the next Green Revolution. The use of gibberellin-related dwarfing genes significantly increased grain yield during the Green Revolution. Brassinosteroids (BRs) play a vital role in regulating agronomic traits and stress resistance. The potential of BR-related genes in crop improvement has been well demonstrated, positioning BRs as crucial targets for the next agricultural biotechnological revolution. However, BRs exert pleiotropic effects on plants, and thus present both opportunities and challenges for their application. Recent research suggests promising strategies for leveraging BR regulatory molecules for crop improvement, such as exploring function-specific genes, identifying beneficial alleles, inducing favorable mutations, and optimizing spatial hormone distribution. Advancing our understanding of the roles of BRs in plants is imperative to implement these strategies effectively. [ABSTRACT FROM AUTHOR]

Plants modify their root system architecture (RSA) in response to nitrogen (N) deficiency. The plant steroidal hormone, brassinosteroid (BR), plays important roles in root growth and development. This study demonstrates that optimal levels of exogenous BR impact significant increases in lateral root length and numbers in Arabidopsis seedlings under mild N-deficient conditions as compared to untreated seedlings. The impact of BR on RSA was stronger under mild N deficiency than under N-sufficient conditions. The BR effects on RSA were mimicked in dominant mutants of BZR1 and BES1 (bzr1-1D and bes1-D) transcription factors, while the RSA was highly reduced in the BR-insensitive mutant bri1-6, confirming that BR signaling is essential for the development of RSA under both N-sufficient and N-deficient conditions. Exogenous BR and constitutive activity of BZR1 and BES1 in dominant mutants led to enhanced root meristem, meristematic cell number, and cortical cell length. Under mild N deficiency, bzr1-1D displayed higher fresh and dry shoot weights, chlorophyll content, and N levels in the shoot, as compared to the wild type. These results indicate that BR modulates RSA under both N-sufficient and N-deficient conditions via the transcription factors BES1/BZR1 module and confers tolerance to N deficiency.

The activation of BRASSINOSTEROID INSENSITIVE1 (BRI1) and its association with the BRI1 ASSOCIATED RECEPTOR KINASE1 (BAK1) are key steps for the initiation of the BR signaling cascade mediating hypocotyl elongation. Heat shock protein 90 (HSP90) is crucial in the regulation of signaling processes and the activation of hormonal receptors. We report that HSP90 is required for the maintenance of the BRI1 receptor at the plasma membrane (PM) and its association with the BAK1 co-receptor during BL-ligand stimulation. HSP90 mediates BR perception and signal transduction through physical interactions with BRI1 and BAK1, while chaperone depletion resulted in lower levels of BRI1 and BAK1 receptors at the PM and affected the spatial partitioning and organization of BRI1/BAK1 heterocomplexes at the PM. The BRI1/BAK1 interaction relies on the HSP90-dependent activation of the kinase domain of BRI1 which leads to the confinement of the spatial dynamics of the membrane resident BRI1 and the attenuation of the downstream signaling. This is evident by the impaired activation and transcriptional activity of BRI1 EMS SUPPRESSOR 1 (BES1) upon HSP90 depletion. Our findings provide conclusive evidence that further expands the commitment of HSP90 in BR signaling through the HSP90-mediated activation of BRI1 in the control of the BR signaling cascade in plants.

Potato is an important food crop worldwide. Brassinosteroids (BRs) are widely involved in plant growth and development, and BIN2 (brassinosteroid insensitive 2) is the negative regulator of their signal transduction. However, the function of BIN2 in the formation of potato tubers remains unclear. In this study, transgenic methods were used to regulate the expression level of StBIN2 in plants, and tuber related phenotypes were analyzed. The overexpression of StBIN2 significantly increased the number of potatoes formed per plant and the weight of potatoes in transgenic plants. In order to further explore the effect of StBIN2 on the formation of potato tubers, this study analyzed BRs, ABA hormone signal transduction, sucrose starch synthase activity, the expression levels of related genes, and interacting proteins. The results show that the overexpression of StBIN2 enhanced the downstream transmission of ABA signals. At the same time, the enzyme activity of the sugar transporter and the expression of synthetic genes were increased in potato plants overexpressing StBIN2, which also demonstrated the upregulation of sucrose and the expression of the starch synthesis gene. Apparently, StBIN2 affected the conversion and utilization of key substances such as glucose, sucrose, and starch in the process of potato formation so as to provide a material basis and energy preparation for forming potatoes. In addition, StBIN2 also promoted the expression of the tuber formation factors StSP6A and StS6K. Altogether, this investigation enriches the study on the mechanism through which StBIN2 regulates potato tuber formation and provides a theoretical basis for achieving a high and stable yield of potato. [ABSTRACT FROM AUTHOR]

Summary: Modifications of plant architecture can increase planting density, regulate photosynthesis, and improve crop yields. Many basic helix–loop–helix (bHLH) transcription factors participate in the brassinosteroid (BR) signaling pathway and are critical for plant architecture morphogenesis in rice. However, the number of identified bHLH genes suitable for improving production value is still limited.In this study, we cloned Lam1, encoding the typical bHLH transcription factor OsbHLH92. OsbHLH92 knockout (KO) lines exhibit erect leaves. Decreases in the number and size of parenchyma cell layers on the adaxial side of the lamina joint in KO lines were the main reason for the decreased leaf angle. Genetic experiments verify that OsBU1 and its homologs are downstream of OsbHLH92, which is involved in the noncanonical RGA1‐mediated BR signaling pathway.OsbHLH91, an OsbHLH92 homolog, plays both conserved and differentiated roles relative to OsbHLH92. Notably, OsbHLH92‐KO lines show erect leaves without the acquisition of adverse agronomic traits. Moreover, by driving a specific panicle promoter, OsbHLH92 can greatly increase productivity by at least 10%.This study identifies new components of the BR signaling pathway, demonstrates the importance of OsbHLH92 in improving planting density and crop productivity, and broadens our knowledge of typical and atypical bHLH family members in rice. [ABSTRACT FROM AUTHOR]

Constitutive photomorpogenic dwarf (CPD) is a pivotal enzyme gene for brassinolide (BR) synthesis and plays an important role in plant growth, including increasing plant biomass and plant height, elongating cells, and promoting xylem differentiation. However, little is known about the function of the CPD gene in sugar beet. In the current study, we isolated CPD from Beta vulgaris L. (BvCPD), which encodes protein localized in the nucleus, cell membrane, and cell wall. BvCPD was strongly expressed in parenchyma cells and vascular bundles. The transgenic sugar beet overexpressing BvCPD exhibited larger diameter than that of the wild type (WT), which mainly owing to the increased number and size of parenchyma cells, the enlarged lumen and area of vessel in the xylem. Additionally, overexpression of BvCPD increased the synthesis of endogenous BR, causing changes in the content of endogenous auxin (IAA) and gibberellin (GA) and accumulation of cellulose and lignin in cambium 1-4 rings of the taproot. These results suggest that BvCPD can promote the biosynthesis of endogenous BR, improve cell wall components, promote the development of parenchyma cells and vascular bundle, thereby playing an important role in promoting the growth and development of sugar beet taproot. [ABSTRACT FROM AUTHOR]

Brassinosteroids (BRs) are a class of polyhydroxylated steroidal phytohormones that are essential for plant growth and development. Rice BRASSINOSTEROID-INSENSITIVE1 (BRI1)-ASSOCIATED RECEPTOR KINASES (OsBAKs) are plasma membrane-localized receptor kinases belonging to the subfamily of leucine-rich repeat receptor kinases. It has been found that in Arabidopsis, BRs induce the formation of a BRI1–BAK1 heterodimer complex and transmit the cascade signal to BRASSINAZOLE RESISTANT1/ bri1 -EMS-SUPPRESSOR1 (BZR1/BES1) to regulate BR signaling. Here, in rice (Oryza sativa ssp. japonica), we found that OsBZR1 binds directly to the promoter of OsBAK2 , but not OsBAK1 , and represses the expression of OsBAK2 to form a BR feedback inhibition loop. Additionally, the phosphorylation of OsBZR1 by OsGSK3 reduced its binding to the OsBAK2 promoter. The osbak2 mutant displays a typical BR-deficiency phenotype and negative modulates the accumulation of OsBZR1. Interestingly, the grain length of the osbak2 mutant was increased whereas in the cr-osbak2 / cr-osbzr1 double mutant, the reduced grain length of the cr-osbzr1 mutant was restored, implying that the increased grain length of osbak2 may be due to the rice somatic embryogenesis receptor kinase-dependent pathway. Our study reveals a novel mechanism by which OsBAK2 and OsBZR1 engage in a negative feedback loop to maintain rice BR homeostasis, facilitating a deeper understanding of the BR signaling network and grain length regulation in rice. [ABSTRACT FROM AUTHOR]

Summary: Brassinosteroids (BRs) are a group of plant‐specific steroid hormones, which induces the rapid nuclear localization of the positive transcriptional factors BRASSINAZOLE RESISTANT1/2 (BZR1/2). However, the mechanisms underlying the regulation of nucleocytoplasmic shuttling of BZR1 remain to be fully elucidated.In this study, we show that the scaffold protein Receptor for Activated C Kinase 1 (RACK1) from Arabidopsis is involved in BR signaling cascades through mediating the nuclear localization of BZR1, which is tightly retained in the cytosol by the conserved scaffold protein 14‐3‐3s.RACK1 can interact with BZR1 and competitively decrease the 14‐3‐3 interaction with BZR1 in cytosol, which efficiently enhances the nuclear localization of BZR1. 14‐3‐3 also retains RACK1 in cytosol through their interaction. Conversely, BR treatment enhances the nuclear localization of BZR1 by disrupting the 14‐3‐3 interaction with RACK1 and BZR1.Our study uncovers a new mechanism that integrates two kinds of conserved scaffold proteins (RACK1 and 14‐3‐3) coordinating BR signaling event. [ABSTRACT FROM AUTHOR]

Abstract Background Genetic variation in regulatory sequences that alter transcription factor (TF) binding is a major cause of phenotypic diversity. Brassinosteroid is a growth hormone that has major effects on plant phenotypes. Genetic variation in brassinosteroid-responsive cis-elements likely contributes to trait variation. Pinpointing such regulatory variations and quantitative genomic analysis of the variation in TF-target binding, however, remains challenging. How variation in transcriptional targets of signaling pathways such as the brassinosteroid pathway contributes to phenotypic variation is an important question to be investigated with innovative approaches. Results Here, we use a hybrid allele-specific chromatin binding sequencing (HASCh-seq) approach and identify variations in target binding of the brassinosteroid-responsive TF ZmBZR1 in maize. HASCh-seq in the B73xMo17 F1s identifies thousands of target genes of ZmBZR1. Allele-specific ZmBZR1 binding (ASB) has been observed for 18.3% of target genes and is enriched in promoter and enhancer regions. About a quarter of the ASB sites correlate with sequence variation in BZR1-binding motifs and another quarter correlate with haplotype-specific DNA methylation, suggesting that both genetic and epigenetic variations contribute to the high level of variation in ZmBZR1 occupancy. Comparison with GWAS data shows linkage of hundreds of ASB loci to important yield and disease-related traits. Conclusion Our study provides a robust method for analyzing genome-wide variations of TF occupancy and identifies genetic and epigenetic variations of the brassinosteroid response transcription network in maize.

IQ67-domain (IQD) proteins function in plant defense and in organ development. The mechanisms by which they influence cotton fiber development are unknown. In the present study, GhIQD10 was expressed mainly in the transition period of cotton fiber development, and GhIQD10-overexpression lines showed shorter fibers. GhIQD10 interacted with GhCaM7 and the interaction was inhibited by Ca2+. In in vitro ovule culture, Ca2+ rescued the shorter-fiber phenotype of GhIQD10-overexpression lines, which were insensitive to the Ca2+ channel inhibitor verapamil and the Ca2+ pool release channel blocker 2-aminoethoxydiphenyl borate. We conclude that GhIQD10 affects cotton fiber elongation via Ca2+ signaling by interacting with GhCaM7. Brassinosteroid (BR) biosynthesis and signaling genes were up-regulated in GhIQD10-overexpression lines. Fiber development in these lines was not affected by epibrassinolide or the BR biosynthesis inhibitor brassinozole, indicating that the influence of GhIQD10 on fiber elongation was not associated with BR.

Xinjiang cotton is characterized by high-density planting, which easily leads to competition between the source and sink, the shading of leaves and reproductive organs, and yield reduction. Balancing the relationship between source and sink can promote high and stable cotton yield. In this study, field experiments were conducted by combining the exogenous application of brassinosteroid with a reduction in leaf source to study their effects on the physiological and yield attributes of cotton. The results indicate that brassinosteroid application increased the yield, with a maximum yield increase of 6.3%. The number of bolls per plant increased by 1.3 nos. The photosynthetic rate and dry matter accumulation were enhanced, and the proportion of reproductive organs in the dry matter increased by >4%. Under the reduced leaf source, brassinosteroid application increased the number of new leaves by 20%, delayed the shedding of reproductive organs by 5–10 days, and reduced the average shedding rate by 8.9%. Additionally, the number of bolls increased in the middle and upper parts and at the edge of the plant. The number of bolls increased by 19.4% on the 4th–8th fruiting branches and 60.7% at the edge. Under leaf reduction treatment, brassinosteroid application could generally increase yield. After brassinosteroid application and removing half the leaves of fruiting branches and all leaves of the vegetive branches, the yield was higher than that of the control. Thus, brassinosteroid application could improve the efficiency of the leaf source and promote dry matter accumulation in sinks. Moreover, it could optimize boll distribution and increase yield by reducing reproductive organ shedding. Under the high-density planting of cotton in Xinjiang, leaf source is a slight surplus, and a moderate reduction in plant density is conducive to increasing yield.