BACKGROUND: The brassinosteroid (BR) plant hormones regulate numerous developmental processes, including those determining stem height, leaf angle, and grain size that have agronomic relevance in cereals. Indeed, barley (Hordeum vulgare) varieties containing uzu alleles that impair BR perception through mutations in the BR receptor BRASSINOSTEROID INSENSITIVE 1 (BRI1) exhibit a semi-dwarf growth habit and more upright leaves suitable for high-density planting. We used forward and reverse genetic approaches to develop novel BRI1 alleles in wheat (Triticum aestivum L.) and investigated their potential for crop productivity improvement. RESULTS: The combination of ethyl methanesulfonate-induced mutations introducing premature stop codons in all three homoeologous TaBRI1 genes resulted in severe dwarfism, malformed leaves and sterility as observed in bri1 mutants in other species. Double mutants had reduced flag-leaf angles (FLAs) conferring a more upright canopy but exhibited no differences in height or grain weight. In a targeted forward genetics screen using a double mutant, we identified two BR-insensitive lines with reduced height and FLA that contained amino acid substitutions in conserved regions of BRI-A1. The less severe mutant had a 56% reduction in FLA and was 35% shorter than the wild type, although seed set, seed area and grain weights were also reduced. The most severe mutants contained elevated levels of bioactive BRs and increased expression of BR-biosynthesis genes consistent with reduced feedback suppression of biosynthesis. CONCLUSION: Our study gives a better understanding of BRI1 function in wheat and provides mutants that could potentially be explored for improving grain yields when sown at high density.

• Klíčová slova
• BR insensitivity, Brassinosteroids, EMS-mutagenesis, Semi-dwarf, Upright leaf angles, Wheat,
• MeSH
• brassinosteroidy metabolismus   MeSH
• fenotyp MeSH
• listy rostlin genetika   anatomie a histologie   růst a vývoj   MeSH
• mutace MeSH
• pšenice * genetika   anatomie a histologie   růst a vývoj   metabolismus   MeSH
• rostlinné proteiny * genetika   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• brassinosteroidy MeSH
• rostlinné proteiny * MeSH

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
• brassinosteroidy * metabolismus   biosyntéza   MeSH
• ječmen (rod) * genetika   metabolismus   růst a vývoj   MeSH
• jedlá semena * genetika   růst a vývoj   MeSH
• mutace genetika   MeSH
• regulace genové exprese u rostlin MeSH
• rostlinné proteiny * genetika   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• brassinosteroidy * MeSH
• rostlinné proteiny * 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.

• Klíčová slova
• TILLING, barley, biosynthesis, brassinosteroids, grain size, plant architecture, plant reproduction,
• Publikační typ
• časopisecké články MeSH

Water availability is undoubtedly one of the most important environmental factors affecting crop production. Drought causes a gradual deprivation of water in the soil from top to deep layers and can occur at diverse stages of plant development. Roots are the first organs that perceive water deficit in soil and their adaptive development contributes to drought adaptation. Domestication has contributed to a bottleneck in genetic diversity. Wild species or landraces represent a pool of genetic diversity that has not been exploited yet in breeding program. In this study, we used a collection of 230 two-row spring barley landraces to detect phenotypic variation in root system plasticity in response to drought and to identify new quantitative trait loci (QTL) involved in root system architecture under diverse growth conditions. For this purpose, young seedlings grown for 21 days in pouches under control and osmotic-stress conditions were phenotyped and genotyped using the barley 50k iSelect SNP array, and genome-wide association studies (GWAS) were conducted using three different GWAS methods (MLM GAPIT, FarmCPU, and BLINK) to detect genotype/phenotype associations. In total, 276 significant marker-trait associations (MTAs; p-value (FDR)< 0.05) were identified for root (14 and 12 traits under osmotic-stress and control conditions, respectively) and for three shoot traits under both conditions. In total, 52 QTL (multi-trait or identified by at least two different GWAS approaches) were investigated to identify genes representing promising candidates with a role in root development and adaptation to drought stress.

• Klíčová slova
• GWAS, QTL, barley landraces, candidate gene, osmotic stress, root system architecture,
• Publikační typ
• časopisecké články MeSH

The objective of this study was to answer the question of how the deacclimation process affects frost tolerance, photosynthetic efficiency, brassinosteroid (BR) homeostasis and BRI1 expression of winter oilseed rape. A comparative study was conducted on cultivars with different agronomic and physiological traits. The deacclimation process can occur when there are periods of higher temperatures, particularly in the late autumn or winter. This interrupts the process of the acclimation (hardening) of winter crops to low temperatures, thus reducing their frost tolerance and becoming a serious problem for agriculture. The experimental model included plants that were non-acclimated, cold acclimated (at 4 °C) and deacclimated (at 16 °C/9 °C, one week). We found that deacclimation tolerance (maintaining a high frost tolerance despite warm deacclimating periods) was a cultivar-dependent trait. Some of the cultivars developed a high frost tolerance after cold acclimation and maintained it after deacclimation. However, there were also cultivars that had a high frost tolerance after cold acclimation but lost some of it after deacclimation (the cultivars that were more susceptible to deacclimation). Deacclimation reversed the changes in the photosystem efficiency that had been induced by cold acclimation, and therefore, measuring the different signals associated with photosynthetic efficiency (based on prompt and delayed chlorophyll fluorescence) of plants could be a sensitive tool for monitoring the deacclimation process (and possible changes in frost tolerance) in oilseed rape. Higher levels of BR were characteristic of the better frost-tolerant cultivars in both the cold-acclimated and deacclimated plants. The relative expression of the BRI1 transcript (encoding the BR-receptor protein) was lower after cold acclimation and remained low in the more frost-tolerant cultivars after deacclimation. The role of brassinosteroids in oilseed rape acclimation/deacclimation is briefly discussed.

• Klíčová slova
• brassinosteroid insensitive 1, brassinosteroids, dehardening, delayed chlorophyll fluorescence, frost tolerance, homocastasterone, photosystem I, photosystem II, prompt chlorophyll fluorescence, stress tolerance,
• MeSH
• aklimatizace fyziologie   MeSH
• Brassica napus * genetika   MeSH
• brassinosteroidy MeSH
• fotosyntéza MeSH
• homeostáza MeSH
• nízká teplota MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• brassinosteroidy MeSH

Brassinosteroids (BRs) are a class of steroid phytohormones, which regulate various processes of morphogenesis and physiology-from seed development to regulation of flowering and senescence. An accumulating body of evidence indicates that BRs take part in regulation of physiological reactions to various stress conditions, including drought. Many of the physiological functions of BRs are regulated by a complicated, and not fully elucidated network of interactions with metabolic pathways of other phytohormones. Therefore, the aim of this study was to characterize phytohormonal homeostasis in barley (Hordeum vulgare) in reaction to drought and validate role of BRs in regulation of this process. Material of this study included the barley cultivar "Bowman" and five Near-Isogenic Lines (NILs) representing characterized semi-dwarf mutants of several genes encoding enzymes participating in BR biosynthesis and signaling. Analysis of endogenous BRs concentrations in these NILs confirmed that their phenotypes result from abnormalities in BR metabolism. In general, concentrations of 18 compounds, representing various classes of phytohormones, including brassinosteroids, auxins, cytokinins, gibberellins, abscisic acid, salicylic acid and jasmonic acid were analyzed under control and drought conditions in the "Bowman" cultivar and the BR-deficient NILs. Drought induced a significant increase in accumulation of the biologically active form of BRs-castasterone in all analyzed genotypes. Another biologically active form of BRs-24-epi-brassinolide-was identified in one, BR-insensitive NIL under normal condition, but its accumulation was drought-induced in all analyzed genotypes. Analysis of concentration profiles of several compounds representing gibberellins allowed an insight into the BR-dependent regulation of gibberellin biosynthesis. The concentration of the gibberellic acid GA7 was significantly lower in all NILs when compared with the "Bowman" cultivar, indicating that GA7 biosynthesis represents an enzymatic step at which the stimulating effect of BRs on gibberellin biosynthesis occurs. Moreover, the accumulation of GA7 is significantly induced by drought in all the genotypes. Biosynthesis of jasmonic acid is also a BR-dependent process, as all the NILs accumulated much lower concentrations of this hormone when compared with the "Bowman" cultivar under normal condition, however the accumulation of jasmonic acid, abscisic acid and salicylic acid were significantly stimulated by drought.

• Klíčová slova
• barley, brassinosteroids, drought, homeostasis, mutants, phytohormones,
• Publikační typ
• časopisecké články MeSH

Brassinosteroids (BRs) are plant steroid hormones, regulating a broad range of physiological processes. The largest amount of data related with BR biosynthesis has been gathered in Arabidopsis thaliana, however understanding of this process is far less elucidated in monocot crops. Up to now, only four barley genes implicated in BR biosynthesis have been identified. Two of them, HvDWARF and HvBRD, encode BR-6-oxidases catalyzing biosynthesis of castasterone, but their relation is not yet understood. In the present study, the identification of the HvDWARF genomic sequence, its mutational and functional analysis and characterization of new mutants are reported. Various types of mutations located in different positions within functional domains were identified and characterized. Analysis of their impact on phenotype of the mutants was performed. The identified homozygous mutants show reduced height of various degree and disrupted skotomorphogenesis. Mutational analysis of the HvDWARF gene with the "reverse genetics" approach allowed for its detailed functional analysis at the level of protein functional domains. The HvDWARF gene function and mutants' phenotypes were also validated by measurement of endogenous BR concentration. These results allowed a new insight into the BR biosynthesis in barley.

• Klíčová slova
• barley, biosynthesis, brassinosteroids, mutant, reverse-genetics, semi-dwarf, splicing,
• MeSH
• alely MeSH
• Arabidopsis genetika   MeSH
• brassinosteroidy biosyntéza   MeSH
• cholestanoly metabolismus   MeSH
• exony MeSH
• fenotyp MeSH
• homozygot MeSH
• introny MeSH
• ječmen (rod) genetika   fyziologie   MeSH
• molekulární sekvence - údaje MeSH
• mutageneze cílená MeSH
• polymerázová řetězová reakce s reverzní transkripcí MeSH
• proteiny huseníčku chemie   genetika   metabolismus   MeSH
• regulátory růstu rostlin biosyntéza   MeSH
• rostlinné proteiny chemie   genetika   metabolismus   MeSH
• sekvence aminokyselin MeSH
• sekvenční seřazení MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• brassinosteroidy MeSH
• castasterone MeSH Prohlížeč
• cholestanoly MeSH
• proteiny huseníčku MeSH
• regulátory růstu rostlin MeSH
• rostlinné proteiny MeSH