Active Brassinosteroids Research Articles

Brassinosteroids: Relevant Evidence Related to Mitigation of Abiotic and Biotic Stresses in Plants

Extreme events of climate change are increasing, such as droughts and heat waves, causing limitations on growth and yield in relevant food crops, as well as threatening global food security. Brassinosteroids (BRs) are natural or synthetic steroids with significant properties that promote plant growth and development. In the current world scenario, research and solutions that can improve plant tolerance to climate change are strategic to ensure food security. The distinctiveness and novelty of this review lie in its comprehensive and detailed approach to the role of BRs in plants under biotic and abiotic stresses. We consolidate information on the action mechanisms on specific organs, providing detailed experimental conclusions of these plant growth regulators, including also commercial products and concentrations tested aiming to mitigate the adverse effects of the stresses. This practical approach highlights the potential of BRs in agriculture and plant protection against stresses. Additionally, our review presents results with plant models and essential food crops, focusing on multidisciplinary approaches and using physiological, biochemical, nutritional, anatomical and agronomic tools to explain the mechanisms of action of brassinosteroids in plants exposed to abiotic and biotic stresses.

Quantitative evaluation of the biological activity of various brassinosteroids using spiral root induction in rice seeds

Quantitative evaluation of the biological activity of various brassinosteroids using spiral root induction in rice seeds

Brassinosteroid modulates ethylene synthesis and antioxidant metabolism to protect rice (Oryza sativa) against heat stress-induced inhibition of source‒sink capacity and photosynthetic and growth attributes

This study presents an exploration of the efficacy of brassinosteroids (BRs) and ethylene in mediating heat stress tolerance in rice (Oryza sativa). Heat is one of the major abiotic factors that prominently deteriorates rice production by influencing photosynthetic efficiency, source‒sink capacity, and growth traits. The application of BR (0.5 mM) and ethylene (200 μl l−1) either individually and/or in combination was found to alleviate heat stress-induced toxicity by significantly improving photosynthesis, source‒sink capacity and defense systems; additionally, it reduced the levels of oxidative stress markers and ethylene formation. The study revealed the positive influence of BR in promoting plant growth responses under heat stress through its interplay with ethylene biosynthesis and enhanced plant defense systems. Interestingly, treatment with the ethylene biosynthesis inhibitor aminoethoxyvinylglycine (AVG) substantiated that BR application to heat-stressed rice plants enhanced ethylene-dependent pathways to counteract the underlying adversities. Thus, BR action was found to be mediated by ethylene to promote heat tolerance in rice. The present study sheds light on the potential tolerance mechanisms which can ensure rice sustainability under heat stress conditions.

Fenoxycarb, a carbamate insect growth regulator, inhibits brassinosteroid action.

Brassinosteroids (BRs) are steroid hormones that regulate plant growth, development, and stress resistance. In this study, we evaluated the effect of agrochemicals on dark-induced hypocotyl elongation, which is regulated by BRs, to identify novel chemicals that regulate BR action. We found that the juvenile hormone agonist fenoxycarb inhibited dark-induced hypocotyl elongation in Arabidopsis. Treatment with the same class of juvenile hormone agonist, pyriproxyfen, did not affect hypocotyl elongation. Co-treatment with fenoxycarb and BR partly canceled the fenoxycarb-induced hypocotyl suppression. In addition, gene expression analysis revealed that fenoxycarb altered the BR-responsive gene expression. These results indicate that fenoxycarb is a BR action inhibitor.

Metabolismo de nitrogênio em plantas de milho submetidas à deficiencia hidrica, brassinosteróides e azospirillum

Abstract The water deficit in particular, reduces the productivity of vegetable crops. To minimize these harmful effects on agriculture, several agronomic and physiological practices are being studied, such as the use of bacteria and water stress attenuators, such as brassinosteroids. Considering the socioeconomic relevance of corn culture and its sensitivity when exposed to water deficit, the objective of the present study was to evaluate the action of brassinosteroids and azospirillum on nitrogen metabolism in corn plants subjected to water stress conditions. The experiment was carried out in a greenhouse, in a period of 47 days, with corn plants, using the hybrid K9606 VIP3. The design was completely randomized, in a 2x2x3 factorial scheme, with six replications. The first factor corresponds to two water regimes (presence and absence of water deficit). The second corresponds to inoculation via seed of Azospirillum brasiliense and absence of inoculation. And the third corresponds to the application of three concentrations of brassinosteroids (0, 0.3 and 0.6 μM). Were determined Nitrate; nitrate reductase; free ammonium; total soluble aminoacids; soluble proteins; proline; glycine betaine and glutamine synthetase. The lack of water in plants provided a reduction in the protein and nitrate reductase contents, in leaves and roots. For ammonium, plants with water deficit inoculated at a concentration of 0.3 μM, obtained an increase of 7.16 (70.26%) and 13.89 (77.04%) mmol NH4 + .Kg-1. DM (Dry mass) on the leaf and root respectively. The water deficit in the soil provided significant increases in the concentrations of glycine betaine, nitrate, proline and aminoacids, both in the leaves and in the roots of the corn plants. On the other hand, the contents of glutamine synthetase had a reduction in both leaves and roots.

The Effect of Phytohormonal Steroids in Combination with Succinic Acid on the Resistance of Hordeum Vulgare L. to Helminthosporium teres Sacc.

Aim: The aim of this investigation is study the BS effect on the growth of Helminthosporium teres Sacc. and to elucidate the protective effect of brassinosteroids and their tetrahemisuccinates on spring barley (Hordeum Vulgare L.) exposed to biotic stress caused by this phytopathogenic fungus. Background: Brassinosteroids and their tetrahemisuccinates are considered as protectors of the fungal infection caused by H.teres. Objective: Evaluation of the effect of brassinosteroids, their mixtures and conjugates with succinic acid against the pathogen H.teres, as well as in spring barley crops against a natural infectious background. Methods: The fungistatic activity of brassinosteroids and their tetrahemisuccinates was evaluated in relation to the phytopathogenic fungus H.teres. The effect of BS and their derivatives on the processes of adaptation of spring barley plants to the pathogen of net spotting of the phytopathogenic fungus H.teres was studied on a model pathosystem and in the agrocenosis. Results: A fungistatic activity of the synthesized substances was revealed, which consists in inhibiting the growth of the phytopathogenic fungus H.teres on a solid nutrient medium by 35-40%. Succinic acid can enhance the fungistatic effect of brassinosteroids, which is more noticeable when using conjugates with succinic acid than in mechanical mixtures. In field experiments, it was shown that the studied compounds and their mixtures applied as a single spraying in the beginning of tubing phase reduced the development of leaf spots caused by phytopathogenic fungi. Conclusion: The results obtained indicate that brassinosteroids with succinic acid both in the form of conjugates and mechanical mixtures show fungistatic activity.

The interplay of auxin and brassinosteroid signaling tunes root growth under low and different nitrogen forms.

The coordinated signaling activity of auxin and brassinosteroids (BRs) is critical for optimal plant growth and development. Nutrient-derived signals regulate root growth by modulating the levels and spatial distribution of growth hormones to optimize nutrient uptake and assimilation. However, the effect of the interaction of these two hormones and their signaling on root plasticity during low and differential availability of nitrogen (N) forms (NH4+/NO3-) remains elusive. We demonstrate that root elongation under low N (LN) is an outcome of the interdependent activity of auxin and BR signaling pathways in Arabidopsis (Arabidopsis thaliana). LN promotes root elongation by increasing BR-induced auxin transport activity in the roots. Increased nuclear auxin signaling and its transport efficiency have a distinct impact on root elongation under LN conditions. High auxin levels reversibly inhibit BR signaling via BRI1 KINASE INHIBITOR1. Using the tissue-specific approach, we show that BR signaling from root vasculature (stele) tissues is sufficient to promote cell elongation and, hence, root growth under LN condition. Further, we show that N form-defined root growth attenuation or enhancement depends on the fine balance of BR and auxin signaling activity. NH4+ as a sole N source represses BR signaling and response, which in turn inhibits auxin response and transport, whereas NO3- promotes root elongation in a BR signaling-dependent manner. In this study, we demonstrate the interplay of auxin and BR-derived signals, which are critical for root growth in a heterogeneous N environment and appear essential for root N foraging response and adaptation.

Stylar steroids: Brassinosteroids regulate pistil development and self-incompatibility in Primula

Manipulation of active brassinosteroid content in the developing flower of Primula dictates style length and female incompatibility type. A new study reveals the dual effects of brassinosteroids on establishing both the morphology of the pistil and mate recognition in self-incompatible heterostylous Primula forbseii.

Genome-wide superior alleles, haplotypes and candidate genes associated with tolerance on sodic-dispersive soils in wheat (Triticum aestivum L.)

Key messageThe pleiotropic SNPs/haplotypes, overlapping genes (metal ion binding, photosynthesis), and homozygous/biallelic SNPs and transcription factors (HTH myb-type and BHLH) hold great potential for improving wheat yield potential on sodic-dispersive soils.Sodic-dispersive soils have multiple subsoil constraints including poor soil structure, alkaline pH and subsoil toxic elemental ion concentration, affecting growth and development in wheat. Tolerance is required at all developmental stages to enhance wheat yield potential on such soils. An in-depth investigation of genome-wide associations was conducted using a field phenotypic data of 206 diverse Focused Identification of Germplasm Strategy (FIGS) wheat lines for two consecutive years from different sodic and non-sodic plots and the exome targeted genotyping by sequencing (tGBS) assay. A total of 39 quantitative trait SNPs (QTSs), including 18 haplotypes were identified on chromosome 1A, 1B, 1D, 2A, 2B, 2D, 3A, 3B, 5A, 5D, 6B, 7A, 7B, 7D for yield and yield-components tolerance. Among these, three QTSs had common associations for multiple traits, indicating pleiotropism and four QTSs had close associations for multiple traits, within 32.38 Mb. The overlapping metal ion binding (Mn, Ca, Zn and Al) and photosynthesis genes and transcription factors (PHD-, Dof-, HTH myb-, BHLH-, PDZ_6-domain) identified are known to be highly regulated during germination, maximum stem elongation, anthesis, and grain development stages. The homozygous/biallelic SNPs having allele frequency above 30% were identified for yield and crop establishment/plants m−2. These SNPs correspond to HTH myb-type and BHLH transcription factors, brassinosteroid signalling pathway, kinase activity, ATP and chitin binding activity. These resources are valuable in haplotype-based breeding and genome editing to improve yield potential on sodic-dispersive soils.

Brassinosteroids regulate petal spur length in Aquilegia by controlling cell elongation.

Aquilegia produce elongated, three-dimensional petal spurs that fill with nectar to attract pollinators. Previous studies have shown that the diversity of spur length across the Aquilegia genus is a key innovation that is tightly linked with its recent and rapid diversification into new ranges, and that evolution of increased spur lengths is achieved via anisotropic cell elongation. Previous work identified a brassinosteroid response transcription factor as being enriched in the early developing spur cup. Brassinosteroids are known to be important for cell elongation, suggesting that brassinosteroid-mediated response may be an important regulator of spur elongation and potentially a driver of spur length diversity in Aquilegia. In this study, we investigated the role of brassinosteroids in the development of the Aquilegia coerulea petal spur. We exogenously applied the biologically active brassinosteroid brassinolide to developing petal spurs to investigate spur growth under high hormone conditions. We used virus-induced gene silencing and gene expression experiments to understand the function of brassinosteroid-related transcription factors in A. coerulea petal spurs. We identified a total of three Aquilegia homologues of the BES1/BZR1 protein family and found that these genes are ubiquitously expressed in all floral tissues during development, yet, consistent with the previous RNAseq study, we found that two of these paralogues are enriched in early developing petals. Exogenously applied brassinosteroid increased petal spur length due to increased anisotropic cell elongation as well as cell division. We found that targeting of the AqBEH genes with virus-induced gene silencing resulted in shortened petals, a phenotype caused in part by a loss of cell anisotropy. Collectively, our results support a role for brassinosteroids in anisotropic cell expansion in Aquilegia petal spurs and highlight the brassinosteroid pathway as a potential player in the diversification of petal spur length in Aquilegia.

Transformation of Endophytic Bipolaris spp. Into Biotrophic Pathogen Under Auxin Cross-Talk With Brassinosteroids and Abscisic Acid.

Auxin is the reciprocal signaling molecule, which interferes with other phyto-hormonal and physiological processes during plant–microbes interaction. In this regard, Bipolaris spp., a growth-promoting endophytic fungus was used to inoculate pre-stressed Zea mays seedlings with yucasin (IAA inhibitor). The IAA-deficient host was heavily colonized by the endophyte that subsequently promoted the host growth and elevated the IAA levels with a peak value at 72 h. However, the seedling growth was inhibited later (i.e., at 120 h) due to the high levels of IAA that interfered with the activity of phytoalexins and brassinosteroids. Such interference also modulated the endophytic fungus from symbiotic to biotrophic pathogen that left the host plants defenseless.

Phytohormonal activity of lactone-structure brassinosteroids under chemical stress in plants

The dependence of the action of lactone-structure brassinosteroids in composition with a growth-inhibiting dose of glyphosate on the root system and the aerial part of fiber flax (Linum usitatissimum L.) and spring barley (Hordeum vulgare L.) seedlings was determined. The species specificity of growth responses to seed incrustation by such mixtures was identified. The concentration ranges of brassinosteroids, in which their interaction with the herbicide is most pronounced, were detected. In this case, there is an increase (on spring barley seedlings) or weakening (on fiber flax seedlings) of the inhibitory effect of glyphosate on the root system.

Effect of Lactone- and Ketone-Containing Brassinosteroids on Photosynthetic Activity of Barley Leaves during Aging

A comparison was made of the physiological activity of brassinosteroids (BS) of different chemical structures—lactone-containing 24-epibrassinolide (EBL) and ketone-containing brassinosteroid 24-epicastasterone (ECS)—during dark aging of cut barley (Hordeum vulgare L.) leaves. The functional state of the photosynthetic apparatus, the amount of photosynthetic pigments, the content of lipid peroxidation products, and gene expression of HvS40 (senescence marker) were assessed. The separated barley leaves were incubated on solutions of EBL and ECS in the concentration range of 0.01–1 µM in Petri dishes on filter paper. Synthetic cytokinin 6-benzylaminopurine (BAP) at a 10 μM concentration was used as a positive control, and distilled water was used as a negative control. Petri dishes with leaves were kept in the dark for 5 days. Measurements of the analyzed parameters were carried out on the first, third, and fifth days from the beginning of incubation, mainly in the middle part of the leaf plate. ECS at a concentration of 1 μM reduced oxidative stress by the fifth day of incubation to a greater extent than EBL at a similar concentration. Regarding maintenance of chlorophyll a (Chl a) levels, 24-epicastasterone (1 μM) was more effective than 24-epibrassinolide. It was shown that exogenous brassinosteroids showed a protective effect on the main photochemical processes of the second photosystem during aging of barley leaves. Moreover, when assessing the coefficient of nonphotochemical quenching (qN), indicators of regulated (Y(NPQ)) and nonregulated (Y(NO)) energy dissipation, the ECS showed a more pronounced protective effect for the second photosystem compared to EBL. It was found that treatment with brassinosteroids reduced the level of gene expression of HvS40, a senescence marker on the fifth day of incubation, which was especially characteristic for the ketone-containing brassinosteroid. Thus, it can be concluded that the ketone-containing brassinosteroid not only exhibits high biological activity but, in terms of a number of parameters, is also more effective than the lactone-containing brassinosteroid in reducing the damage caused by aging.

Seed-Specific Expression of Arabidopsis AtCYP85A2 Produces Biologically Active Brassinosteroids Such as Castasterone and Brassinolide to Improve Grain Yield and Quality in Seeds of Brachypodium Distachyon

Brachypodium distachyon is a monocotyledonous model plant that contains castasterone (CS) but no brassinolide (BL) as the end product of brassinosteroids (BR) biosynthesis, indicating dysfunction of BL synthase, which catalyzes the conversion of CS to BL. To increase BR activity, Arabidopsis cytochrome P450 85A2 (AtCYP85A2) encoding BR 6-oxidase/BL synthase was introduced into B. distachyon with the seed-specific promoters pBSU1, pAt5g10120, and pAt5g54000. RT-PCR analysis and GUS activity revealed that AtCYP85A2 was only expressed in the seeds of the transgenic plants pBSU1-AtCYP85A2::Bd21-3, pAt5g10120-AtCYP85A2::Bd21-3, and pAt5g54000-AtCYP85A2::Bd21-3. The crude enzyme prepared from the seeds of these three transgenic plants catalyzed the conversion of 6-deoxoCS to CS. The transgenic plants showed greater specific enzyme activity than the wild-type plant for the conversion of 6-deoxoCS to CS, indicating enhanced BR 6-oxidase activity in the transgenic plants. The enzyme solution also catalyzed the conversion of CS into BL. Additionally, BL was identified from the seeds of transgenic plants, verifying that seed-specific AtCYP85A2 encodes a functional BL synthase to increase BR activity in the seeds of transgenic Brachypodium. In comparison with wild-type Brachypodium, the transgenic plants showed better growth and development during the vegetative growing stage. The flowers of the transgenic plants were remarkably larger, resulting in increments in the number, size, and height of seeds. The total starch, protein, and lipid contents in transgenic plants were higher than those in wild-type plants, indicating that seed-specific expression of AtCYP85A2 improves both grain yield and quality in B. distachyon.

Roles of Brassinosteroids in Mitigating Heat Stress Damage in Cereal Crops.

Heat stress causes huge losses in the yield of cereal crops. Temperature influences the rate of plant metabolic and developmental processes that ultimately determine the production of grains, with high temperatures causing a reduction in grain yield and quality. To ensure continued food security, the tolerance of high temperature is rapidly becoming necessary. Brassinosteroids (BR) are a class of plant hormones that impact tolerance to various biotic and abiotic stresses and regulate cereal growth and fertility. Fine-tuning the action of BR has the potential to increase cereals’ tolerance and acclimation to heat stress and maintain yields. Mechanistically, exogenous applications of BR protect yields through amplifying responses to heat stress and rescuing the expression of growth promoters. Varied BR compounds and differential signaling mechanisms across cereals point to a diversity of mechanisms that can be leveraged to mitigate heat stress. Further, hormone transport and BR interaction with other molecules in plants may be critical to utilizing BR as protective agrochemicals against heat stress. Understanding the interplay between heat stress responses, growth processes and hormone signaling may lead us to a comprehensive dogma of how to tune BR application for optimizing cereal growth under challenging environments in the field.

Proteomics for Brassinosteroid signalling: Understanding Brassinosteroids mediated stress responses through advanced proteomics

Brassinosteroids (BRs), class of steroidal phytohormones have a crucial role in various physiological mechanisms and involved in plant defense against different biotic and abiotic stresses. Understanding BRs action mechanism is very critical to promote plant development and boosting agricultural productivity. The mechanism of BRs action and signalling pathway is very intricate which requires exploration through various tools and techniques. Phytoproteomics had revealed the many cellular modifications induced via BRs signalling and identified potential functional metabolites involved in plant adaptation to stress conditions under BRs application. Additionally, proteomics provided the insights of activation events of receptor kinases and downregulation of various components via phosphorylation which cannot be analyzed by the genomics tools. So, the knowledge gap about the BRs signalling can be filled through various advanced proteomics tools that increase the applications of BRs in agricultural practices. This review summarizes the recent developments in knowledge of BRs signalling mechanism using various phytoproteomics tools.

Synthesis of New Brassinosteroid 24-Norcholane Type Analogs Conjugated in C-3 with Benzoate Groups.

The metabolism of brassinosteroid leads to structural modifications in the ring skeleton or the side alkyl chain. The esterification and glycosylation at C-3 are the most common metabolic pathways, and it has been suggested that conjugate brassinosteroids are less active or inactive. In this way, plants regulate the content of active brassinosteroids. In this work, the synthesis of brassinosteroid 24-norcholane type analogs conjugated at C-3 with benzoate groups, carrying electron donor and electron attractant substituents on the aromatic ring, is described. Additionally, their growth-promoting activities were evaluated using the Rice Lamina Inclination Test (RLIT) and compared with that exhibited by brassinolide (used as positive control) and non-conjugated analogs. The results indicate that at the lowest tested concentrations (10−8–10−7 M), all analogs conjugated at C-3 exhibit similar or higher activities than brassinolide, and the diasteroisomers with S configuration at C-22 are the more active ones. Increasing concentration (10−6 M) reduces the biological activities of analogs as compared to brassinolide.

24-epibrassinolide-induced growth promotion of wheat seedlings is associated with changes in the proteome and tyrosine phosphoproteome.

Brassinosteroids (BRs) represent a unique class of steroidal plant hormones that display pronounced growth-promoting activity at very low concentrations. Although many efforts have been made to characterize the molecular basis of BR action, little is known about the mechanisms behind the growth-promoting effect of BRs at protein level. Proteomic analysis of response to the steroid plant hormone 24-epibrassinolide (EBR) in wheat seedling shoots (Triticum aestivum L.) was performed using two-dimensional electrophoresis (2-DE) and immunoblotting with highly specific antibodies (PY20) to phosphotyrosine. EBR-modulated proteins and phosphotyrosine polypeptides were identified using MALDI-TOF mass spectrometry. The study revealed that EBR-stimulated growth of wheat seedlings was accompanied by changes in the content of multiple proteins as well as in tyrosine phosphorylation of numerous polypeptides. Among them, 22 differentially accumulated proteins and 13 phosphotyrosine proteins were identified. Based on their performed functions, the identified proteins are involved in physiological processes (photosynthesis, growth, energy and amino acid metabolism) closely associated with intensification of plant metabolism. The EBR-induced changes in protein abundance and tyrosine phosphorylation profile may contribute to growth stimulation of wheat seedlings under the action of EBR. The obtained data suggest an important role for EBR in the activation of protein metabolism underlying fundamental physiological processes, including growth promotion.

Effect of brassinoesteroid hormone on oxidants activity of two contrasting cowpea cultivars subjected to saline stress

The aims of this study were to study the biochemical metabolism alterations generated by saline stress in two cowpea cultivars: BRS Guariba (moderately tolerant) and BR3 Tracuateua (sensitive), and to investigate the action of brassinosteroid in attenuation of oxidative stress. The results for water content and damage index in cell membranes were similar. Plants with 24-Epibrassinolide hormone maintained their water content satisfactory and without any membrane extravasation, whereas, for plants with salinity these variables decreased considerably. The results showed that salinity increased sodium (Na+) contents and reduced potassium (K+) content, which caused water increases allowing a higher dilution of sodium ions (Na+), avoiding cellular toxicity. The antioxidant defense system of these plants (catalase, superoxide dismutase, ascorbate peroxidase, and guaiacol peroxidase) were activated mainly in characterization of salt stress, increasing their concentrations trying to avoid toxicity. The association of brassine and salinity caused reduction of lipid peroxidation characterized by malondialdehyde variable. These results corroborated the efficacy of the brassine hormone in cowpea plants under saline stress, characterizing as a plant plasticity.

Brassinosteroids in Plant Tolerance to Abiotic Stress

Brassinosteroids (BRs) are a group of plant steroid hormones with multiple roles in plant growth, development, and responses to stresses. In plants, BR deficiencies impair vital physiological processes and cause phenotypic abnormalities. A large number of studies show that BRs can positively influence plant responses to abiotic stresses such as heat, cold, drought, salinity, pesticides, and heavy metals. However, the underlying mechanisms of BR-induced stress tolerance are largely unclear. BR perception takes place in the cell surface by BR receptors, leading to a cascade of phosphorylation events to activate the central transcription factor BRASSINAZOLE-RESISTANT1 (BZR1) that controls the transcription of BR-responsive genes in the nucleus. BRs improve photosynthetic efficiency under stress conditions, which largely contributes to increased growth and biomass accumulation. Studies relating to exogenous BRs reveal a high dependency on concentrations with regards to BR effects on plants. Genetic studies show a positive correlation between the endogenous BR levels and abiotic stress tolerance, although this assumption contradicts with the performance of some BR mutants under stress conditions. Notably, plant responses to BRs greatly vary depending on the plant species, developmental stages, and environmental conditions. In addition, other hormones and signaling molecules that participate in fine-tuning the BRs effects also play an important role in plant adaptation to stress. Here, we review the involvement of BRs in plant responses to abiotic stresses. We also discuss available literature to show potential mechanisms of BR-induced abiotic stress tolerance. These studies signify the complexity of BR action in mediating stress responses in plants.