Brassinosteroids (BRs) are phytohormones which regulate various developmental processes in plants. They are exceptional phytohormones, as they do not undergo long-distance transport between plant organs. However, knowledge about the function of the enzymes that catalyse BR biosynthesis (particularly its early stages) in cereal crops remains limited. Therefore, this study identifies and analyses the function of the HvDWARF5 (HvDWF5) gene, involved in the early stage of BR biosynthesis in barley (Hordeum vulgare), an important cereal crop, using the TILLING (Targeting Induced Local Lesions IN Genomes) approach. The detailed functional analysis allowed for the identification of various mutations in different gene fragments. The influence of these mutations on plant architecture, reproduction, and yield was characterised. Moreover, effects of the missense and intron retention mutations on sequence and splicing of the HvDWF5 transcript, sequence and predicted structure of the encoded HvDWF5 enzyme, and accumulation of endogenous BR were determined. Some of the barley mutants identified in this study showed semi-dwarfism, a trait of particular importance for cereal breeding and yield. However, unlike other BR mutants in cereals, this did not negatively affect grain size or weight. It indicated that mutations in this gene allow for a balance between plant height reduction and maintenance of grain size. Thus, the results of this study provide a novel insight into the role of the HvDWF5 gene in the BR biosynthesis-dependent regulation of architecture and reproduction of the important cereal crop - barley.

• MeSH
• Brassinosteroids * metabolism   biosynthesis   MeSH
• Hordeum * genetics   metabolism   growth & development   MeSH
• Edible Grain * genetics   growth & development   MeSH
• Mutation genetics   MeSH
• Gene Expression Regulation, Plant MeSH
• Plant Proteins * genetics   metabolism   MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Brassinosteroids * MeSH
• Plant Proteins * MeSH

Brassinosteroids (BRs) are steroid phytohormones which regulate various physiological and developmental processes throughout plant life cycle. The BR biosynthesis has been studied mainly in the dicot model species - Arabidopsis thaliana. However, our current understanding of the BR biosynthesis and its regulation in other species, including cereal crops, is limited. Functions of enzymes which catalyze early stages of the BR biosynthesis in cereals remain poorly understood. Moreover, mechanisms regulating expression of genes encoding these enzymes remain obscure. One of the genes which participate in the early stages of the BR biosynthesis in Arabidopsis is STE1 (STEROL DESATURASE1). However, detailed functional analyses of this gene and its promoter region have not been performed. The aim of this study was to identify and functionally analyze the STE1 gene in barley (Hordeum vulgare) which is an important cereal crop. The functional analysis was carried out with the application of TILLING (Targeting Induced Local Lesions IN Genomes) approach. Six mutations were identified within the 1st exon (including three located in the 5'UTR region) and one missense mutation was identified in the 2nd exon of HvSTE1. Effects of the identified alleles on the HvSTE1 gene expression, sequence of the encoded enzyme variants, BR accumulation, as well as on stature, agronomic traits, and reproduction of the identified mutants were characterized. Homozygous mutants carrying two alleles (hvste1.b and hvste1.o) displayed reduced plant height and defects in the BR accumulation. The HvSTE1 expression was considerably decreased in the 3rd internode of the hvste1.b mutant. Interestingly, the hvste1.b mutant plants showed semi-dwarf phenotype without any negative effect on crucial agronomic traits, such as tiller number, spike length, and grain weight. Moreover, weight of grains produced by the hvste1.b mutant was slightly (5%) higher when compared with the reference cultivar. The results of this study provided a novel insight into the function of the HvSTE1 gene in the BR biosynthesis-dependent regulation of architecture and reproduction of barley. Moreover, the hvste1.b allele allows for achieving a balance between the favorable alteration in plant architecture (semi-dwarfism) and maintenance (slight improvement) of grain weight in this species.

• Keywords
• TILLING, barley, biosynthesis, brassinosteroids, grain size, plant architecture, plant reproduction,
• Publication type
• Journal Article MeSH

Exogenously applied brassinosteroids (BRs) improve plant response to drought. However, many important aspects of this process, such as the potential differences caused by different developmental stages of analyzed organs at the beginning of drought, or by BR application before or during drought, remain still unexplored. The same applies for the response of different endogenous BRs belonging to the C27, C28-and C29- structural groups to drought and/or exogenous BRs. This study examines the physiological response of two different leaves (younger and older) of maize plants exposed to drought and treated with 24-epibrassinolide (epiBL), together with the contents of several C27, C28-and C29-BRs. Two timepoints of epiBL application (prior to and during drought) were utilized to ascertain how this could affect plant drought response and the contents of endogenous BRs. Marked differences in the contents of individual BRs between younger and older maize leaves were found: the younger leaves diverted their BR biosynthesis from C28-BRs to C29-BRs, probably at the very early biosynthetic steps, as the levels of C28-BR precursors were very low in these leaves, whereas C29-BR levels vere extremely high. Drought also apparently negatively affected contents of C28-BRs (particularly in the older leaves) and C29-BRs (particularly in the younger leaves) but not C27-BRs. The response of these two types of leaves to the combination of drought exposure and the application of exogenous epiBL differed in some aspects. The older leaves showed accelerated senescence under such conditions reflected in their reduced chlorophyll content and diminished efficiency of the primary photosynthetic processes. In contrast, the younger leaves of well-watered plants showed at first a reduction of proline levels in response to epiBL treatment, whereas in drought-stressed, epiBL pre-treated plants they were subsequently characterized by elevated amounts of proline. The contents of C29- and C27-BRs in plants treated with exogenous epiBL depended on the length of time between this treatment and the BR analysis regardless of plant water supply; they were more pronounced in plants subjected to the later epiBL treatment. The application of epiBL before or during drought did not result in any differences of plant response to this stressor.

• Keywords
• OJIP analysis, brassinosteroids, drought, endogenous content, exogenous application, leaf age, proline,
• Publication type
• Journal Article MeSH

Drought is one of the major abiotic stresses affecting the productivity of Brassica crops. To understand the role of phytohormones in drought tolerance, we subjected Chinese cabbage (B. rapa ssp. pekinensis), white cabbage (B. oleracea var. capitata), and kale (B. oleracea var. acephala) to drought and examined the stress response on the physiological, biochemical and hormonal levels. The phytohormones abscisic acid (ABA), auxin indole-3-acetic acid (IAA), brassinosteroids (BRs), cytokinins (CKs), jasmonates (JAs), and salicylic acid (SA) were analyzed by ultra-high-performance liquid chromatography⁻tandem mass spectrometry (UHPLC-MS/MS). Based on the physiological and biochemical markers the Chinese cabbage exhibited the lowest tolerance, followed by the white cabbage, while the kale appeared to be the most tolerant to drought. The drought tolerance of the kale correlated with increased levels of SA, ABA, IAA, CKs iP(R) and cZ(R), and typhasterol (TY), a precursor of active BRs. In contrast, the drought sensitivity of the Chinese cabbage correlated with a significant increase in ABA, JAs and the active BRs castasterol (CS) and brassinolide (BL). The moderately tolerant white cabbage, positioned between the kale and Chinese cabbage, showed more similarity in terms of the phytohormone patterns with the kale. We concluded that the drought tolerance in Brassicaceae is mostly determined by the increased endogenous levels of IAA, CKs, ABA and SA and the decreased levels of active BRs.

• Keywords
• Brassica crops, drought, phytohormones, recovery, tolerance,
• MeSH
• Brassica classification   genetics   metabolism   MeSH
• Stress, Physiological * MeSH
• Droughts * MeSH
• Gene Expression Regulation, Plant * MeSH
• Plant Growth Regulators metabolism   MeSH
• Plant Proteins genetics   metabolism   MeSH
• Gene Expression Profiling MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Plant Growth Regulators MeSH
• Plant Proteins MeSH

The contents of endogenous brassinosteroids (BRs) together with various aspects of plant morphology, water management, photosynthesis and protection against cell damage were assessed in two maize genotypes that differed in their drought sensitivity. The presence of 28-norbrassinolide in rather high quantities (1-2 pg mg-1 fresh mass) in the leaves of monocot plants is reported for the first time. The intraspecific variability in the presence/content of the individual BRs in drought-stressed plants is also described for the first time. The drought-resistant genotype was characterised by a significantly higher content of total endogenous BRs (particularly typhasterol and 28-norbrassinolide) compared with the drought-sensitive genotype. On the other hand, the drought-sensitive genotype showed higher levels of 28-norcastasterone. Both genotypes also differed in the drought-induced reduction/elevation of the levels of 28-norbrassinolide, 28-norcastasterone, 28-homocastasterone and 28-homodolichosterone. The differences observed between both genotypes in the endogenous BR content are probably correlated with their different degrees of drought sensitivity, which was demonstrated at various levels of plant morphology, physiology and biochemistry.

• MeSH
• Brassinosteroids pharmacology   MeSH
• Photosynthesis * MeSH
• Stress, Physiological * MeSH
• Genotype MeSH
• Zea mays drug effects   genetics   growth & development   MeSH
• Plant Leaves drug effects   genetics   growth & development   MeSH
• Droughts * MeSH
• Plant Growth Regulators pharmacology   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Brassinosteroids MeSH
• Plant Growth Regulators MeSH