24-epibrassinolide enhances drought tolerance in grapevine (Vitis vinifera L.) by regulating carbon and nitrogen metabolism.

KEY MESSAGE: Exogenous application of 24-epibrassinolide can alleviate oxidative damage, improve photosynthetic capacity, and regulate carbon and nitrogen assimilation, thus improving the tolerance of grapevine (Vitis vinifera L.) to drought stress. Brassinosteroids (BRs) are a group of plant steroid hormones in plants and are involved in regulating plant tolerance to drought stress. This study aimed to investigate the regulation effects of BRs on the carbon and nitrogen metabolism in grapevine under drought stress. The results indicated that drought stress led to the accumulation of superoxide radicals and hydrogen peroxide and an increase in lipid peroxidation. A reduction in oxidative damage was observed in EBR-pretreated plants, which was probably due to the improved antioxidant concentration. Moreover, exogenous EBR improved the photosynthetic capacity and sucrose phosphate synthase activity, and decreased the sucrose synthase, acid invertase, and neutral invertase, resulting in improved sucrose (190%) and starch (17%) concentrations. Furthermore, EBR pretreatment strengthened nitrate reduction and ammonium assimilation. A 57% increase in nitrate reductase activity and a 13% increase in glutamine synthetase activity were observed in EBR pretreated grapevines. Meanwhile, EBR pretreated plants accumulated a greater amount of proline, which contributed to osmotic adjustment and ROS scavenging. In summary, exogenous EBR enhanced drought tolerance in grapevines by alleviating oxidative damage and regulating carbon and nitrogen metabolism.

Synergistic effects of melatonin and 24-epibrassinolide on chickpea water deficit tolerance.

BACKGROUND: Water deficiency stress reduces yield in grain legumes, primarily due to a decrease in the pods number. Melatonin (ML) and 24-epibrassinolide (EBL) are recognized for their hormone-like properties that improve plant tolerance to abiotic stresses. This study aimed to assess the impact of different concentrations of ML (0, 100, and 200 µM) and EBL (0, 3, and 6 µM) on the growth, biochemical, and physiological characteristics of chickpea plants under water-stressed conditions. RESULTS: The study's findings indicated that under water-stressed conditions, a decrease in seed (30%) and pod numbers (31%), 100-seed weight (17%), total chlorophyll content (46%), stomatal conductance (33%), as well as an increase in H2O2 (62%), malondialdehyde content (40%), and electrolyte leakage index (40%), resulted in a 40% reduction in chickpea plants grain yield. Our findings confirmed that under water-stressed conditions, seed oil, seed oil yield, and seed protein yield dropped by 20%, 55%, and 36%, respectively. The concurrent exogenous application of ML and EBL significantly reduces oxidative stress, plasma membrane damage, and reactive oxygen species (ROS) content. This treatment also leads to increased yield and its components, higher pigment content, enhanced oil and protein yield, and improved enzymatic and non-enzymatic antioxidant activities such as catalase, superoxide dismutase, polyphenol oxidase, ascorbate peroxidase, guaiacol peroxidase, flavonoid, and carotenoid. Furthermore, it promotes the accumulation of osmoprotectants such as proline, total soluble protein, and sugars. CONCLUSIONS: Our study found that ML and EBL act synergistically to regulate plant growth, photosynthesis, osmoprotectants accumulation, antioxidant defense systems, and maintain ROS homeostasis, thereby mitigating the adverse effects of water deficit conditions. ML and EBL are key regulatory network components in stressful conditions, with significant potential for future research and practical applications. The regulation metabolic pathways of ML and EBL in water-stressed remains unknown. As a result, future research should aim to elucidate the molecular mechanisms by employing genome editing, RNA sequencing, microarray, transcriptomic, proteomic, and metabolomic analyses to identify the mechanisms involved in plant responses to exogenous ML and EBL under water deficit conditions. Furthermore, the economical applications of synthetic ML and EBL could be an interesting strategy for improving plant tolerance.

Mitigating Ni and Cu ecotoxicity in the ecological restoration material and ornamental Primula forbesii Franch. with exogenous 24-epibrassinolide and melatonin.

Nickel (Ni) and copper (Cu) contamination have become major threats to plant survival worldwide. 24-epibrassinolide (24-EBR) and melatonin (MT) have emerged as valuable treatments to alleviate heavy metal-induced phytotoxicity. However, plants have not fully demonstrated the potential mechanisms by which these two hormones act under Ni and Cu stress. Herein, this study investigated the impact of individual and combined application of 24-EBR and MT on the growth and physiological traits of Primula forbesii Franch. subjected to stress (200 µmol L-1 Ni and Cu). The experiments compared the effects of different mitigation treatments on heavy metal (HM) stress and the scientific basis and practical reference for using these exogenous substances to improve HM resistance of P. forbesii in polluted environments. Nickel and Cu stress significantly hindered leaf photosynthesis and nutrient uptake, reducing plant growth and gas exchange. However, 24-EBR, MT, and 24-EBR + MT treatments alleviated the growth inhibition caused by Ni and Cu stress, improved the growth indexes of P. forbesii, and increased the gas exchange parameters. Exogenous MT effectively alleviated Ni stress, and 24-EBR + MT significantly alleviated the toxic effects of Cu stress. Unlike HM stress, MT and 24-EBR + MT activated the antioxidant enzyme activity (by increasing superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT)), significantly reduced reactive oxygen species (ROS) accumulation, and regulated ascorbate and glutathione cycle (AsA-GSH) efficiency. Besides, the treatments enhanced the ability of P. forbesii to accumulate HMs, shielding plants from harm. These findings conclusively illustrate the capability of 24-EBR and MT to significantly bolster the tolerance of P. forbesii to Ni and Cu stress.

24-epibrassinolide as a multidimensional regulator of rice (Oryza sativa) physiological and molecular responses under isoproturon stress.

Brassinosteroids (BRs) can regulate various processes in plant development and defense against environmental stress. In this study, the contribution of BRs in the degradation of isoproturon (IPU) in rice has been established. IPU has a significant effect on rice growth, chlorophyll content, and membrane permeability. When treated with 1.0 µmol/L 24-epibrassinolide (EBR), a BR analogue, the associated symptoms of rice poisoning were alleviated as the IPU levels in the rice and growth media were decreased. In the presence of EBR, the activities of several IPU-related detoxification enzymes were enhanced to cope with the stress due to IPU. An RNA-sequencing (RNA-Seq) has been performed to determine the variation of transcriptomes and metabolic mechanisms in rice treated with EBR, IPU, or IPU+EBR. Some of the differentially expressed genes (DEGs) were Phase I-III reaction components of plants, such as cytochrome P450 (CYP450), glutathione S-transferase (GST), glycosyltransferases (GTs), and the ATP-binding cassette transporter (ABC transporter). The expression of some signal transduction genes was significantly up-regulated. The relative content of low-toxicity IPU metabolites increased due to the presence of EBR as determined by UPLC/Q-TOF-MS/MS. The IPU metabolic pathways include enzyme-catalyzed demethylation, hydroxylation, hydrolysis, glycosylation, and amino acid conjugation processes. The results suggest that EBR plays a key role in the degradation and detoxification of IPU. This study has provided evidence that BRs regulate the metabolism and detoxification of IPU in rice, and offers a new approach to ensuring cleaner crops by eliminating pesticide residues in the environment.

BR regulates wheat root salt tolerance by maintaining ROS homeostasis.

MAIN CONCLUSION: Trace amounts of epibrassinolide (EpiBL) could partially rescue wheat root length inhibition in salt-stressed situation by scavenging ROS, and ectopic expression of TaDWF4 or TaBAK1 enhances root salt tolerance in Arabidopsis by balancing ROS level. Salt stress often leads to ion toxicity and oxidative stress, causing cell structure damage and root development inhibition in plants. While prior research indicated the involvement of exogenous brassinosteroid (BR) in plant responses to salt stress, the precise cytological role and the function of BR in wheat root development under salt stress remain elusive. Our study demonstrates that 100 mM NaCl solution inhibits wheat root development, but 5 nM EpiBL partially rescues root length inhibition by decreasing H2O2 content, oxygen free radical (OFR) content, along with increasing the peroxidase (POD) and catalase (CAT) activities in salt-stressed roots. The qRT-PCR experiment also shows that expression of the ROS-scavenging genes (GPX2 and CAT2) increased in roots after applying BR, especially during salt stress situation. Transcriptional analysis reveals decreased expression of BR synthesis and root meristem development genes under salt stress in wheat roots. Differential expression gene (DEG) enrichment analysis highlights the significant impact of salt stress on various biological processes, particularly "hydrogen peroxide catabolic process" and "response to oxidative stress". Additionally, the BR biosynthesis pathway is enriched under salt stress conditions. Therefore, we investigated the involvement of wheat BR synthesis gene TaDWF4 and BR signaling gene TaBAK1 in salt stress responses in roots. Our results demonstrate that ectopic expression of TaDWF4 or TaBAK1 enhances salt tolerance in Arabidopsis by balancing ROS (Reactive oxygen species) levels in roots.

Molecular mechanisms underlying low temperature inhibition of grain filling in maize (Zea mays L.): coordination of growth and cold responses.

Low temperature (LT) greatly restricts grain filling in maize (Zea mays L.), but the relevant molecular mechanisms are not fully understood. To better understand the effect of LT on grain development, 17 hybrids were subjected to LT stress in field trials over 3 years, and two hybrids of them with contrasting LT responses were exposed to 30/20°C and 20/10°C for 7 days during grain filling in a greenhouse. At LT, thousand-kernel weight declined, especially in LT-sensitive hybrid FM985, while grain-filling rate was on average about 48% higher in LT-tolerant hybrid DK159 than FM985. LT reduced starch synthesis in kernel mainly by suppression of transcript levels and enzyme activities for sucrose synthase and hexokinase. Brassinolide (BR) was abundant in DK159 kernel, and genes involved in BR and cytokinin signals were inducible by stress. LT downregulated the genes in light-harvesting complex and photosystem I/II subunits, accompanied by reduced photosynthetic rate and Fv/Fm in ear leaf. The LT-tolerant hybrid could maintain a high soluble sugar content and fast interconversion between sucrose and hexose in the stem internode and cob, improving assimilate allocation to kernel at LT stress and paving the way for simultaneous growth and LT stress responses.

Brassinolide as potential rescue agent for Pinellia ternata grown under microplastic condition: Insights into their modulatory role on photosynthesis, redox homeostasis, and AsA-GSH cycling.

Microplastic (MP), as a new pollutant, not only affects the growth and development of plants but also may affect the secondary metabolites of plants. The anti-tumor role of Pinellia ternata is related to secondary metabolites. The role of brassinolide (BR) in regulating plant resistance is currently one of the research hotspots. The paper mainly explores the regulation of BR on growth and physiology of Pinellia ternata under MP stress. The experimental design includes two levels of MP (0, 1%) and two levels of BR (0, 0.1 mg/L). MP led to a marked reduction in plant height (15.0%), Fv/Fm (3.2%), SOD and APX activity (15.0%, 5.1%), whereas induced an evident raise in the rate of O2·- production (29.6%) and GSH content (4.4%), as well as flavonoids (6.8%), alkaloids (75%), and ß-sitosterol (26.5%) contents. Under MP addition, BR supply significantly increased plant height (15.7%), aboveground and underground biomass (16.1%, 10.3%), carotenoid and GSH content (11.8%, 4.2%), Fv/Fm (2.9%), and activities of SOD, GR, and MDHAR (32.2%, 21.08%, 20.9%). These results indicate that MP suppresses the growth of P. ternata, although it promotes secondary metabolism. BR can alleviate the inhibitory effect of MP on growth by improving photosynthesis, redox homeostasis, and the AsA-GSH cycle.

Sodium nitrophenolate mediates brassinosteroids signaling to enhance cold tolerance of cucumber seedling.

Cold stress (CS) significantly limits cucumber yield. However, it remains unclear whether and how sodium nitrophenolate (CSN) regulates plant responses to cold stress. Here, H2O, CSN, 24-epibrassinolide (EBR), and CSN + EBR were sprayed on cucumber seedlings before or after CS, and on control plants. We found that CSN, EBR, or EBR + CSN pre-treatment improved seedling growth under normal conditions (control condition) and cold tolerance under CS conditions. EBR pre-treatment promoted the expression of approximately half of the genes involved in BR synthesis and signaling and CsICE-CsCBF-CsCOR under CS. However, CSN pre-treatment promoted almost all the expression of BR synthesis and signaling genes, and CsICE-CsCBF-CsCOR genes, which showed the highest expression in early CS, remarkably improving the cold tolerance of cucumber. Interestingly, EBR and CSN had a superimposed effect on the expression of BR synthesis and signaling and CsICE-CsCBF-CsCOR genes, which rapidly increased their expression under normal temperature. Spraying EBR after CS accelerated seedling recovery, whereas CSN had the opposite effect. However, spraying CSN combined with EBR accelerated the recovery of CS-injured seedlings and was better than spraying EBR alone. Although CS-injured seedlings were negatively influenced by CSN, pre-treatment with CSN accelerated seedling growth and increased cold tolerance, suggesting that the effect of CSN was related to whether the seedlings were damaged by CS. In conclusion, we firstly found that CSN enhanced cold tolerance by activating BR signaling, contributing to the gene expression of ICE-CBF-COR and that CSN + EBR contributed to cold tolerance and CS-injured seedling recovery in cucumber.

Assessment of Biological Activity of 28-Homobrassinolide via a Multi-Level Comparative Analysis.

Brassinosteroids (BRs) play vital roles in the plant life cycle and synthetic BRs are widely used to increase crop yield and plant stress tolerance. Among them are 24R-methyl-epibrassinolide (24-EBL) and 24S-ethyl-28-homobrassinolide (28-HBL), which differ from brassinolide (BL, the most active BR) at the C-24 position. Although it is well known that 24-EBL is 10% active as BL, there is no consensus on the bioactivity of 28-HBL. A recent outpouring of research interest in 28-HBL on major crops accompanied with a surge of industrial-scale synthesis that produces mixtures of active (22R,23R)-28-HBL and inactive (22S,23S)-28HBL, demands a standardized assay system capable of analyzing different synthetic "28-HBL" products. In this study, the relative bioactivity of 28-HBL to BL and 24-EBL, including its capacity to induce the well-established BR responses at molecular, biochemical, and physiological levels, was systematically analyzed using the whole seedlings of the wild-type and BR-deficient mutant of Arabidopsis thaliana. These multi-level bioassays consistently showed that 28-HBL exhibits a much stronger bioactivity than 24-EBL and is almost as active as BL in rescuing the short hypocotyl phenotype of the dark-grown det2 mutant. These results are consistent with the previously established structure-activity relationship of BRs, proving that this multi-level whole seedling bioassay system could be used to analyze different batches of industrially produced 28-HBL or other BL analogs to ensure the full potential of BRs in modern agriculture.

Exogenous Brassinosteroid Enhances Zinc tolerance by activating the Phenylpropanoid Biosynthesis pathway in Citrullus lanatus L.

Zinc (Zn) is an important element in plants, but over-accumulation of Zn is harmful. The phytohormone brassinosteroids (BRs) play a key role in regulating plant growth, development, and response to stress. However, the role of BRs in watermelon (Citrullus lanatus L.) under Zn stress, one of the most important horticultural crops, remains largely unknown. In this study, we revealed that 24-epibrassinolide (EBR), a bioactive BR enhanced Zn tolerance in watermelon plants, which was related to the EBR-induced increase in the fresh weight, chlorophyll content, and net photosynthetic rate (Pn) and decrease in the content of hydrogen peroxide (H2O2), malondialdehyde (MDA), and Zn in watermelon leaves. Through RNA deep sequencing (RNA-seq), 350 different expressed genes (DEG) were found to be involved in the response to Zn stress after EBR treatment, including 175 up-regulated DEGs and 175 down-regulated DEGs. The up-regulated DEGs were significantly enriched in 'phenylpropanoid biosynthesis' pathway (map00940) using KEGG enrichment analysis. The gene expression levels of PAL, 4CL, CCR, and CCoAOMT, key genes involved in phenylpropanoid pathway, were significantly induced after EBR treatment. In addition, compared with Zn stress alone, EBR treatment significantly promoted the activities of PAL, 4CL, and POD by 30.90%, 20.69%, and 47.28%, respectively, and increased the content of total phenolic compounds, total flavonoids, and lignin by 23.02%, 40.37%, and 29.26%, respectively. The present research indicates that EBR plays an active role in strengthening Zn tolerance, thus providing new insights into the mechanism of BRs enhancing heavy metal tolerance.

Anti-cancer activity, and molecular docking of novel hybrid heterocyclic steroids revealed promising anti-hepatocellular carcinoma agent: Implication of cyclin dependent kinase-2 pathway.

To identify new steroidal agents with potential biological activities, we synthesized hybrid steroids containing thiazole, pyrazole, isoxazole, thiophene or phthalazine moiety. Epi-androsterone 1 reacted with phenylthiosemicarbazide to afford the corresponding androstane-4-phenyl-3-thiosemicarbazone derivative 2. The latter product was used in the synthesis of a series of annulated steroid derivatives. Also, Epi-androsterone 1 reacted with the thienopyridazine derivative 16 to afford the thieno[3,4-d]pyridazino-N-ylidenoandrostane derivative 17. Compound 17 reacted readily with electron-poor olefins to yield the corresponding phthalazine steroid derivatives. Detailed experimental and spectroscopic evidences for the structures of the newly synthesized compounds are explained. Compounds 3, 7, 8a, 12a, 14, 17 and 21a, were investigated individually as anticancer agents on different panel of human malignant cell lines. Moreover, a computer modelling investigation was performed to speculate the macromolecular targets for the most promising candidate. The results revealed a concentration-dependent reduction in the number of viable cells in all cancer cell lines. Most notably, compound 7 was the most effective compound against all tested cancer cell lines, especially against HepG2 cell line; therefore, the mode of action of this compound against HCC was investigated. Compound 7 was able to induce cell cycle arrest, and DNA fragmentation in HepG2 cells. Moreover, compound 7 induced apoptosis via upregulating the expression of caspase-3, -8, -9, P53, Bax and inhibiting the expression of BCL2, and CDK2 genes. Our results highlighted compound 7 as a promising anti-hepatocellular carcinoma agent, with theoretical, and practical potential binding affinity with CDK2; therefore, more investigations are required to elucidate its chemotherapeutic value as anti-HCC agent.

Formation of nitrogen-containing six-membered heterocycles on steroidal ring system: A review.

Steroidal heterocyclic compounds constitute interesting and promising scaffolds for drug discovery as they have displayed diverse chemical reactivity and several types of biological activities. This study is a concise report on the most recent advancements in the chemistry of the steroid skeleton, including reactions at the A, B, and D ring systems. The modern synthetic methods for the steroidal nitrogen-containing six-membered heterocyclic derivatives from 3-keto-, 6-keto-, 17-keto-, and 20-keto-steroids, as well as 2-Aldo-, 4-Aldo-, 6-Aldo-, and 16-Aldo-steroids, are discussed. However, some other methods for the synthesis of steroidal N-containing 6-membered heterocyclic derivatives are also included. These compounds have shown therapeutic potential as cytotoxic agents against various cell lines and have also shown antiproliferative, anti-inflammatory, and antioxidant activities. Therefore, they could be used as prospective candidates for the development of various medications. This paper not only describes synthetic details involved in creating N-containing 6-membered heterocyclic steroid derivatives, but also provides a brief overview of the medicinal applications of these compounds. This information will be highly useful for the medicinal chemists conducting research in this field.

Cancer and brassinosteroids: Mechanisms of action, SAR and future perspectives.

Brassinosteroids are plant hormones whose main function is to stimulate plant growth. However, they have been studied for their biological applications in humans. Brassinosteroid compounds have displayed an important role in the study of cancer pathology and show potential for developing novel anticancer drugs. In this review we describe the relationship of brassinosteroids with cancer with focus on the last decade, the mechanisms of cytotoxic activity described to date, and a structure-activity relationship based on the available information.

Brassinolide alleviates Fe deficiency-induced stress by regulating the Fe absorption mechanism in Malus hupehensis Rehd.

KEY MESSAGE: Exogenous brassinolide promotes Fe absorption through mechanism I strategy, thus improving the tolerance of Malus hupehensis seedlings to Fe deficiency stress. Iron (Fe) deficiency is a common nutritional disorder that results in decreased yield and poor fruit quality in apple production. As a highly active synthetic analog of brassinosteroids, brassinolide (BL) plays numerous roles in plant responses to abiotic stresses. However, its role in Fe deficiency stress in apple plants has never been reported. Herein, we found that the exogenous application of 0.2 mg L-1 BL could significantly enhance the tolerance of apple seedlings to Fe deficiency stress and result in a low etiolation rate and a high photosynthetic rate. The functional mechanisms of this effect were also explored. We found that first, exogenous BL could improve Fe absorption through the mechanism I strategy. BL induced the activity of H+-ATPase and the expression of MhAHA family genes, resulting in rhizosphere acidification. Moreover, BL could enhance the activity of Fe chelate reductase and absorb Fe through direct binding with the E-box of the MhIRT1 or MhFRO2 promoter via the transcription factors MhBZR1 and MhBZR2. Second, exogenous BL alleviated osmotic stress by increasing the contents of osmolytes (proline, solution proteins, and solution sugar) and scavenged reactive oxygen species by improving the activities of antioxidant enzymes. Lastly, exogenous BL could cooperate with other endogenous plant hormones, such as indole-3-acetic acid, isopentenyl adenosine, and gibberellic acid 4, that respond to Fe deficiency stress indirectly. This work provided a theoretical basis for the application of exogenous BL to alleviate Fe deficiency stress in apple plants.

Structure modification of nonsteroidal brassinolide-like compound, NSBR1.

Brassinolide (BL) is a possible plant growth regulator in agriculture, but the presence of a steroid skeleton hampers the field application of BL in agriculture because of its high synthetic cost. We discovered NSBR1 as the first nonsteroidal BL-like compound using in silico technology. Searching for more potent BL-like compounds, we modified the structure of NSBR1 with respect to 2 benzene rings and the piperazine ring. The activity of synthesized compounds was measured in Arabidopsis hypocotyl elongation. The propyl group of butyryl moiety of NSBR1 was changed to various alkyl groups, such as straight, branched, and cyclic alkyl chains. Another substituent, F, at the ortho position of the B ring toward the piperazine ring was changed to other substituents. A methyl group was introduced to the piperazine ring. Most of the newly synthesized compounds with the 3,4-(OH)2 group at the A ring significantly elongated the hypocotyl of Arabidopsis.

The Mechanisms Underlying Salt Resistance Mediated by Exogenous Application of 24-Epibrassinolide in Peanut.

Peanut is one of the most important oil crops in the world, the growth and productivity of which are severely affected by salt stress. 24-epibrassinolide (EBL) plays an important role in stress resistances. However, the roles of exogenous EBL on the salt tolerance of peanut remain unclear. In this study, peanut seedlings treated with 150 mM NaCl and with or without EBL spray were performed to investigate the roles of EBL on salt resistance. Under 150 mM NaCl conditions, foliar application of 0.1 µM EBL increased the activity of catalase and thereby could eliminate reactive oxygen species (ROS). Similarly, EBL application promoted the accumulation of proline and soluble sugar, thus maintaining osmotic balance. Furthermore, foliar EBL spray enhanced the total chlorophyll content and high photosynthesis capacity. Transcriptome analysis showed that under NaCl stress, EBL treatment up-regulated expression levels of genes encoding peroxisomal nicotinamide adenine dinucleotide carrier (PMP34), probable sucrose-phosphate synthase 2 (SPS2) beta-fructofuranosidase (BFRUCT1) and Na+/H+ antiporters (NHX7 and NHX8), while down-regulated proline dehydrogenase 2 (PRODH). These findings provide valuable resources for salt resistance study in peanut and lay the foundation for using BR to enhance salt tolerance during peanut production.

Comparison of Protective Reactions of Rape Seeds to Chloride Salination at Exposure to Epibrassinolide before or during Salt Stress.

We compared the defensive response of rape plants to treatment with 24-epibrassinoldide (10 nM, EBL) before the onset of salt stress (preadaptation stage) and under conditions of chloride salination (150 mM NaCl). It is shown that salt stress inhibits some growth parameters by 30-35%. EBL, regardless of the plant treatment method, showed a pronounced protective effect, first of all, at the level of the assimilating surface, the main photosynthetic pigments, and the photochemical activity of photosystem II. It was established for the first time that the pretreatment of plants with EBL followed by salt stress is accompanied by suppression of NaCl-induced accumulation of proline and an increase in superoxide dismutase activity, whereas the addition of a hormone under salt stress increases the content of carotenoids, which leads to a decrease in the level of lipid peroxidation.

Pistil Mating Type and Morphology Are Mediated by the Brassinosteroid Inactivating Activity of the S-Locus Gene BAHD in Heterostylous Turnera Species.

Heterostyly is a breeding system that promotes outbreeding through a combination of morphological and physiological floral traits. In Turnera these traits are governed by a single, hemizygous S-locus containing just three genes. We report that the S-locus gene, BAHD, is mutated and encodes a severely truncated protein in a self-compatible long homostyle species. Further, a self-compatible long homostyle mutant possesses a T. krapovickasii BAHD allele with a point mutation in a highly conserved domain of BAHD acyl transferases. Wild type and mutant TkBAHD alleles were expressed in Arabidopsis to assay for brassinosteroid (BR) inactivating activity. The wild type but not mutant allele caused dwarfism, consistent with the wild type possessing, but the mutant allele having lost, BR inactivating activity. To investigate whether BRs act directly in self-incompatibility, BRs were added to in vitro pollen cultures of the two mating types. A small morph specific stimulatory effect on pollen tube growth was found with 5 µM brassinolide, but no genotype specific inhibition was observed. These results suggest that BAHD acts pleiotropically to mediate pistil length and physiological mating type through BR inactivation, and that in regard to self-incompatibility, BR acts by differentially regulating gene expression in pistils, rather than directly on pollen.

Epibrassinolide improves the growth performance of Sedum lineare upon Zn stress through boosting antioxidative capacities.

As an essential element, zinc (Zn) can improve or inhibit the growth of plants depending on its concentrations. In this study, the effects of 24-Epibrassinolide (EBR), one well-known steroid phytohormone regulating plant growth and alleviating abiotic stress damage, on morphological parameters and antioxidant capacities of Sedum lineare were investigated under different Zn doses. Compared to plants only exposed to Zn, simultaneously foliar application of 0.75 µM EBR significantly improved multiple morphological characteristics and such growth-improving effects were more significant at high Zn concentrations. At a detrimental 800 µM Zn, EBR benefitted plant growth most prominently, as shown by that the stem length, fresh weight and internode length were increased by 111%, 85% and 157%, respectively; than Zn solely treated plants. EBR spray also enhanced both the activities of antioxidant enzymes such as peroxidase (POD), ascorbate peroxidase (APX), glutathione reductase (GR), and the contents of antioxidative agents including ascorbic acid (AsA) and glutathione (GSH), which in turn decreased the accumulation of reactive oxygen species (ROS) and alleviated the lipid peroxidation in plants. Thus, by demonstrating that EBR could help S. lineare resist high-zinc stress through strengthening the antioxidant system, this work provided a new idea for expanding the planting range of Crassulaceae plants in heavy metal contaminated soil for phytoremediation purpose in the future.

Epibrassinolide prevents tau hyperphosphorylation via GSK3ß inhibition in vitro and improves Caenorhabditis elegans lifespan and motor deficits in combination with roscovitine.

Glycogen synthase kinase 3ß (GSK3ß) is considered an important element of glycogen metabolism; however, it has many other regulatory roles. Changes in the GSK3ß signaling mechanism have been associated with various disorders, such as Alzheimer's disease (AD), type II diabetes, and cancer. Although the effects of GSK3ß inhibitors on reducing the pathological effects of AD have been described, an effective inhibitor has not yet been developed. Epibrassinolide (EBR), a brassinosteroid (BR), is structurally similar to mammalian steroid hormones. Our studies have shown that EBR has an inhibitory effect on GSK3ß in different cell lines. Roscovitine (ROSC), a cyclin-dependent kinase (CDK) inhibitor, has also been identified as a potential GSK3 inhibitor. Within the scope of this study, we propose that EBR and/or ROSC might have mechanistic action in AD models. To test this hypothesis, we used in vitro models and Caenorhabditis elegans (C. elegans) AD strains. Finally, EBR treatment successfully protected cells from apoptosis and increased the inhibitory phosphorylation of GSK3ß. In addition, EBR and/or ROSC treatment had a positive effect on the survival rates of C. elegans strains. More interestingly, the paralysis phenotype of the C. elegans AD model due to Aß42 toxicity was prevented by EBR and/or ROSC. Our findings suggest that EBR and ROSC administration have neuroprotective effects on both in vitro and C. elegans models via inhibitory GSK3ß phosphorylation at Ser9.