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Results for “brassinosteroid”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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15 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Final Report: Proteomic study of brassinosteroid responses in Arabidopsis

The steroid hormone brassinosteroid (BR) is a major growth-promoting phytohormone. The specific aim of the current project is to identify BR-regulated proteins and characterize their functions in various aspects of plant growth, development, and adaptation. Our research has significantly advanced our understanding of how BR signal is transduced from the receptor at the cell surface to changes of nuclear gene expression and other cellular responses such as vesicle trafficking, as well as developmental transitions such as seed germination and flowering. We have also developed effective proteomic methods for quantitative analysis of protein phosphorylation and for identification of glycosylated proteins. Through this DOE funding, we have performed several proteomic experiments and made major discoveries.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

Brassinosteroid reduces ABA accumulation leading to the inhibition of ABA-induced stomatal closure

Highlights: • ABA strengthened BL-induced stomatal closure. • Expression of OST1 was induced by BL, and BL-induced stomatal closure required OST1. • Inhibition of ABA-induced stomatal closure by BR was due to reduced ABA accumulation. Proper regulation of stomatal movement in response to various environmental stresses or developmental status is critical for the adaptation of many plant species to land. In plants, abscisic acid (ABA)-induced stomatal closure is a well-adapted method of regulating water status. In addition to ABA, we previously showed that plant-specific steroidal hormone, brassinosteroid (BR), also induces stomatal closure; however, BR modulates ABA-induced stomatal closure negatively at high concentrations. In this study, we further investigated the cross-talk between ABA and BR in relation to stomatal movement. In contrast to previous reports that ABA-induced stomatal closure was inhibited by brassinolide (BL), the most active BR, we showed that BL-induced stomatal closure was enhanced by ABA, indicating that the sequence of ABA or BL treatments led to different results. We found that this phenomenon occurred because the guard cells still had the capacity to be closed further by ABA, as the degree of stomatal closure by BL was always less than that by ABA. We also found that BL-induced stomatal closure required Open Stomata 1 (OST1) activity and the induced expression of OST1 was indifferent to the sequence of ABA and/or BL treatments. In addition, we examined the underlying mechanism by which inhibition of ABA-induced stomatal closure by BL occurred. We revealed that the downregulation of ABA-biosynthetic genes by BL resulted in a lower accumulation of ABA. These results suggested that the regulation of stomatal movement is finely controlled by the combined effects of plant hormones, ABA and BR.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2024

A maize semi-dwarf mutant reveals a GRAS transcription factor involved in brassinosteroid signaling

Brassinosteroids (BR) and gibberellins (GA) regulate plant height and leaf angle in maize (Zea mays). Mutants with defects in BR or GA biosynthesis or signaling identify components of these pathways and enhance our knowledge about plant growth and development. In this study, we characterized three recessive mutant alleles of GRAS transcription factor 42 (gras42) in maize, a GRAS transcription factor gene orthologous to the DWARF AND LOW TILLERING (DLT) gene of rice (Oryza sativa). These maize mutants exhibited semi-dwarf stature, shorter and wider leaves, and more upright leaf angle. Transcriptome analysis revealed a role for GRAS42 as a determinant of BR signaling. Analysis of the expression consequences from loss of GRAS42 in the gras42-mu1021149 mutant indicated a weak loss of BR signaling in the mutant, consistent with its previously demonstrated role in BR signaling in rice. Loss of BR signaling was also evident by the enhancement of weak BR biosynthetic mutant alleles in double mutants of nana plant1-1 and gras42-mu1021149. The gras42-mu1021149 mutant had little effect on GA-regulated gene expression, suggesting that GRAS42 is not a regulator of core GA signaling genes in maize. Single-cell expression data identified gras42 expressed among cells in the G2/M phase of the cell cycle consistent with its previously demonstrated role in cell cycle gene expression in Arabidopsis (Arabidopsis thaliana). Cis-acting natural variation controlling GRAS42 transcript accumulation was identified by expression genome-wide association study (eGWAS) in maize. Our results demonstrate a conserved role for GRAS42/SCARECROW-LIKE 28 (SCL28)/DLT in BR signaling, clarify the role of this gene in GA signaling, and suggest mechanisms of tillering and leaf angle control by BR.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2016

‘Candidatus Liberibacter asiaticus’, causal agent of citrus Huanglongbing, is reduced by treatment with Brassinosteroids

Huanglongbing (HLB) constitutes the most destructive disease of citrus worldwide, yet no established efficient management measures exist for it. Brassinosteroids, a family of plant steroidal compounds, are essential for plant growth, development and stress tolerance. As a possible control strategy for HLB, epibrassinolide was applied to as a foliar spray to citrus plants infected with the causal agent of HLB, ‘Candidatus Liberibacter asiaticus’. The bacterial titers were reduced after treatment with epibrassinolide under both greenhouse and field conditions but were stronger in the greenhouse. Known defense genes were induced in leaves by epibrassinolide. With the SuperSAGE technology combined with next generation sequencing, induction of genes known to be associated with defense response to bacteria and hormone transduction pathways were identified. Lastly, the results demonstrate that epibrassinolide may provide a useful tool for the management of HLB.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

High-throughput quantitative analysis of phytohormones in sorghum leaf and root tissue by ultra-performance liquid chromatography-mass spectrometry

Plant development, growth, and adaptation to stress are regulated by phytohormones, which can influence physiology even at low concentrations. Phytohormones are chemically grouped according to both structure and function as auxins, cytokinins, abscisic acid, jasmonates, salicylates, gibberellins, and brassinosteroids, among others. This chemical diversity and requirement for highly sensitive detection in complex matrices create unique challenges for comprehensive phytohormone analysis. Here, we present a robust and efficient quantitative UPLC-MS/MS assay for 17 phytohormones, including jasmonates, salicylates, abscisic acid, gibberellins, cytokinins, and auxins. Using this assay, 12 phytohormones were detected and quantified in sorghum plant tissue without the need for solid phase extraction (SPE) or liquid-liquid extraction. Variation of phytohormone profiles was explored in both root and leaf tissues between three genotypes, harvested at two different developmental time points. The results highlight the importance of tissue type, sampling time, and genetic factors when designing experiments that involve phytohormone analysis of sorghum. This research lays the groundwork for future studies, which can combine phytohormone profiling with other datasets such as transcriptome, soil microbiome, genome, and metabolome data, to provide important functional information about adaptation to stress and other environmental variables.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Structure of maize BZR1-type β-amylase BAM8 provides new insights into its noncatalytic adaptation

Plant β-amylase (BAM) proteins play an essential role in growth, development, stress response, and hormone regulation. Despite their typical (β/α) 8 barrel structure as active catalysts in starch breakdown, catalytically inactive BAMs are implicated in diverse yet elusive functions in plants. Further, the noncatalytic BAM7/8 contain N-terminal BZR1 domains and were shown to be involved in the regulation of brassinosteroid signaling and possibly serve as sensors of yet an uncharacterized metabolic signal. While the structures of several catalytically active BAMs have been reported, structural characterization of the catalytically inactive BZR1-type BAMs remain unknown. Here, we determine the crystal structure of β-amylase domain of Zea mays BAM8/BES1/BZR1-5 and provide comprehensive insights into its noncatalytic adaptation. Using structural-guided comparison combined with biochemical analysis and molecular dynamics simulations, we revealed conformational changes in multiple distinct highly conserved regions resulting in rearrangement of the binding pocket. Altogether, this study adds a new layer of understanding to starch breakdown mechanism and elucidates the acquired adjustments of noncatalytic BZR1-type BAMs as putative regulatory domains and/or metabolic sensors in plants.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Structure and growth of plant cell walls

Plant cells build nanofibrillar walls that are central to plant growth, morphogenesis and mechanics. Starting from simple sugars, three groups of polysaccharides, namely, cellulose, hemicelluloses and pectins, with very different physical properties are assembled by the cell to make a strong yet extensible wall. Here, this Review describes the physics of wall growth and its regulation by cellular processes such as cellulose production by cellulose synthase, modulation of wall pH by plasma membrane H + -ATPase, wall loosening by expansin and signalling by plant hormones such as auxin and brassinosteroid. In addition, this Review discusses the nuanced roles, properties and interactions of cellulose, matrix polysaccharides and cell wall proteins and describes how wall stress and wall loosening cooperatively result in cell wall growth.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2016

Chemical Biology And Endomembrane Trafficking In Plants

Endomembrane trafficking is essential for coordinated growth and development in plants and response to environment. In particular, key plasma membrane proteins such as PIN auxin transporters and the BRI1 brassinosteroid receptor translocate dynamically between the endosomes and plasma membrane. We utilized a previously published large‐scale chemical library screening approach in which we identified small molecules that inhibited pollen germination or tube growth. This tip growth requires exocytosis, endocytosis and other endomembrane trafficking processes We then identified groups of small molecules that affect trafficking of PIN auxin transporters and other plasma membrane proteins in Arabidopsis roots. One of these compounds (ES2) targets the essential EXO70A1 component of the exocyst complex in Arabidopsis which is necessary for normal development. In Arabidopsis, there are 23 EXO70 genes (in mammals and yeast they are low copy number) where, among other roles, they appear to be involved in autophagy, cell division and pathogen responses. ES2 targets the exocyst complex in plants as well as mammals including humans where defective recycling/exocytosis have been correlated with disease. To our knowledge, ES2 is the first bioactive compound known to have this specificity. To examine exocytosis and its regulation in more detail, we have examined exo70 mutants, generated EXO70A1 structural data and are examining additional small molecules that may affect recycling/exocytosis. Support or Funding Information Acknowledgement: This work was supported by the US Department of Energy DE‐FG02‐02ER15295 (GRH, NVR).

Hicks, Glenn R.↗
DOE OSTI2020

The AGCVIII kinase Dw2 modulates cell proliferation, endomembrane trafficking, and MLG/xylan cell wall localization in elongating stem internodes of Sorghum bicolor

Stems of bioenergy sorghum (Sorghum bicolor L. Moench.), a drought–tolerant C4 grass, contain up to 50 nodes and internodes of varying length that span 4–5 m and account for approximately 84% of harvested biomass. Stem internode growth impacts plant height and biomass accumulation and is regulated by brassinosteroid signaling, auxin transport, and gibberellin biosynthesis. In addition, an AGCVIII kinase (Dw2) regulates sorghum stem internode growth, but the underlying mechanism and signaling network are unknown. Here we provide evidence that mutation of Dw2 reduces cell proliferation in internode intercalary meristems, inhibits endocytosis, and alters the distribution of heteroxylan and mixed linkage glucan in cell walls. Phosphoproteomic analysis showed that Dw2 signaling influences the phosphorylation of proteins involved in lipid signaling (PLDδ), endomembrane trafficking, hormone, light, and receptor signaling, and photosynthesis. Altogether, our results show that Dw2 modulates endomembrane function and cell division during sorghum internode growth, providing insight into the regulation of monocot stem development.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

GhBZR3 suppresses cotton fiber elongation by inhibiting very‐long‐chain fatty acid biosynthesis

SUMMARY The BRASSINAZOLE‐RESISTANT (BZR) transcription factor is a core component of brassinosteroid (BR) signaling and is involved in the development of many plant species. BR is essential for the initiation and elongation of cotton fibers. However, the mechanism of BR‐regulating fiber development and the function of BZR is poorly understood in Gossypium hirsutum L. (cotton). Here, we identified a BZR family transcription factor protein referred to as GhBZR3 in cotton. Overexpression of GhBZR3 in Arabidopsis caused shorter root hair length, hypocotyl length, and hypocotyl cell length, indicating that GhBZR3 negatively regulates cell elongation. Pathway enrichment analysis from VIGS ‐GhBZR3 cotton plants found that fatty acid metabolism and degradation might be the regulatory pathway that is primarily controlled by GhBZR3. Silencing GhBZR3 expression in cotton resulted in taller plant height as well as longer fibers. The very‐long‐chain fatty acid (VLCFA) content was also significantly increased in silenced GhBZR3 plants compared with the wild type. The GhKCS13 promoter, a key gene for VLCFA biosynthesis, contains two GhBZR3 binding sites. The results of yeast one‐hybrid, electrophoretic mobility shift, and luciferase assays revealed that GhBZR3 directly interacted with the GhKCS13 promoter to suppress gene expression. Taken together, these results indicate that GhBZR3 negatively regulates cotton fiber development by reducing VLCFA biosynthesis. This study not only deepens our understanding of GhBZR3 function in cotton fiber development, but also highlights the potential of improving cotton fiber length and plant growth using GhBZR3 and its related genes in future cotton breeding programs.

Shi, Zemin↗
DOE OSTI2022

Bioenergy sorghum stem growth regulation: intercalary meristem localization, development, and gene regulatory network analysis

SUMMARY Bioenergy sorghum is a highly productive drought tolerant C 4 grass that accumulates 80% of its harvestable biomass in approximately 4 m length stems. Stem internode growth is regulated by development, shading, and hormones that modulate cell proliferation in intercalary meristems (IMs). In this study, sorghum stem IMs were localized above the pulvinus at the base of elongating internodes using magnetic resonance imaging, microscopy, and transcriptome analysis. A change in cell morphology/organization occurred at the junction between the pulvinus and internode where LATERAL ORGAN BOUNDARIES ( SbLOB ), a boundary layer gene, was expressed. Inactivation of an AGCVIII kinase in DDYM ( dw2 ) resulted in decreased SbLOB expression, disrupted IM localization, and reduced internode cell proliferation. Transcriptome analysis identified approximately 1000 genes involved in cell proliferation, hormone signaling, and other functions selectively upregulated in the IM compared with a non‐meristematic stem tissue. This cohort of genes is expressed in apical dome stem tissues before localization of the IM at the base of elongating internodes. Gene regulatory network analysis identified connections between genes involved in hormone signaling and cell proliferation. The results indicate that gibberellic acid induces accumulation of growth regulatory factors (GRFs) known to interact with ANGUSTIFOLIA (SbAN3), a master regulator of cell proliferation. GRF:AN3 was predicted to induce SbARF3/ETT expression and regulate SbAN3 expression in an auxin‐dependent manner. GRFs and ARFs regulate genes involved in cytokinin and brassinosteroid signaling and cell proliferation. The results provide a molecular framework for understanding how hormone signaling regulates the expression of genes involved in cell proliferation in the stem IM.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2017

Involvement of PACLOBUTRAZOL RESISTANCE6/KIDARI, an Atypical bHLH Transcription Factor, in Auxin Responses in Arabidopsis

Auxin regulates nearly all aspects of plant growth and development including cell division, cell elongation and cell differentiation, which are achieved largely by rapid regulation of auxin response genes. However, the functions of a large number of auxin response genes remain uncharacterized. Paclobutrazol Resistance (PRE) proteins are non-DNA binding basic helix-loop-helix transcription factors that have been shown to be involved in gibberellin and brassinosteroid signaling, and light responses in Arabidopsis. Here, we provide molecular and genetic evidence that PRE6, one of the six PRE genes in Arabidopsis, is an auxin response gene, and that PRE6 is involved in the regulation of auxin signaling. By using quantitative RT-PCR, we showed that the expression level of PRE6 was increased in response to exogenously applied IAA. GUS staining results also showed that the expression of GUS reporter gene in the PRE6p:GUS transgenic seedlings was elevated in response to auxin. Phenotypic analysis showed that overexpression of PRE6 in Arabidopsis resulted in auxin-related phenotypes including elongated hypocotyl and primary roots, and reduced number of lateral roots when compared with the Col wild type seedlings, whereas opposite phenotypes were observed in the pre6 mutants. Further analysis showed that PRE6 overexpression plants were hyposensitive, whereas pre6 mutants were hypersensitive to auxin in root and hypocotyl elongation and lateral root formation assays. By using protoplasts transfection, we showed that PRE6 functions as a transcriptional repressor. Consistent with this, the expression of the auxin response reporter DR5:GUS was decreased in PRE6 overexpression lines, but increased in pre6 mutants. When co-transfected into protoplasts, ARF5 and ARF8 activated the expression of the PRE6p:GUS reporter. Chromatin immunoprecipitation assays showed that ARF5 and ARF8 can be recruited to the promoter regions of PRE6. Taken together, these results suggest that PRE6 is an auxin response gene whose expression is directly regulated by ARF5 and ARF8, and that PRE6 is a transcriptional repressor that negatively regulates auxin responses in Arabidopsis.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Over-Expression of a Maize N-Acetylglutamate Kinase Gene ( ZmNAGK ) Improves Drought Tolerance in Tobacco

Water deficit is a key limiting factor that affects the growth, development and productivity of crops. It is vital to understand the mechanisms by which plants respond to drought stress. Here an N -acetylglutamate kinase gene, ZmNAGK , was cloned from maize ( Zea mays ). ZmNAGK was expressed at high levels in maize leaves and at lower levels in root, stem, female flower and male flower. The expression of ZmNAGK was significantly induced by PEG, NaCl, ABA, brassinosteroid and H 2 O 2 . The ectopic expression of ZmNAGK in tobacco resulted in higher tolerance to drought compared to plants transformed with empty vector. Further physiological analysis revealed that overexpression of ZmNAGK could enhance the activities of antioxidant defense enzymes, and decrease malondialdehyde content and leakage of electrolyte in tobacco under drought stress. Moreover, the ZmNAGK transgenic tobacco accumulated more arginine and nitric oxide (NO) than control plants under drought stress. In addition, the ZmNAGK transgenic tobaccos activated drought responses faster than vector-transformed plants. Here, these results indicate that ZmNAGK can play a vital role in enhancing drought tolerance by likely affecting the arginine and NO accumulation, and ZmNAGK could be involved in different strategies in response to drought stress.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1995

Arabidopsis TCH4, regulated by hormones and the environment, encodes a xyloglucan endotransglycosylase

Adaptation of plants to environmental conditions requires that sensing of external stimuli be linked to mechanisms of morphogenesis. The Arabidopsis TCH (for touch) genes are rapidly upregulated in expression in response to environmental stimuli, but a connection between this molecular response and developmental alterations has not been established. We identified TCH4 as a xyloglucan endotransglycosylase by sequence similarity and enzyme activity. Xyloglucan endotransglycosylases most likely modify cell walls, a fundamental determinant of plant form. We determined that TCH4 expression is regulated by auxin and brassinosteroids, by environmental stimuli, and during development, by a 1-kb region. Expression was restricted to expanding tissues and organs that undergo cell wall modification. Regulation of genes encoding cell wall-modifying enzymes, such as TCH4, may underlie plant morphogenetic responses to the environment.

NASA Discipline Plant Biology↗