Study On The Redox Regulation Of BRS1 In Arabidopsis Thaliana

Plants are the major photosynthetic species providing carbohydrate assimilates for heterotrophic organisms by converting solar energy to chemical energy. At the same time, plants have evolved complicated regulation mechanism to cope with various biotic and abiotic stresses in the environment due to sessile growth. The most significant stress response is the burst of reactive oxygen species(ROS). ROS is not only a chemical molecules causing redox state changes, but also a signal molecule to transduce environmental stimulus enabling plants to response accurately.Changes of redox status will affect the growth and development of plants. Therefore, underlying the mechanism of plant redox state regulation is important for plant stress tolerance improvement tightly with agricultural production.Brassinosteroids(BRs) is a kind of important steroid hormones involved in the regulation of growth and development of plant. BRI1 is the main receptor of BR, previous study found a weak mutant of BRI1 extracellular domain, bri1-5. Using the activation tagging method we obtain a bri1-5 recovery line, functional analysis reveals the phenotype possibly correlate with BRS1 and finally the gene is cloned. BRS1 is a serine type II protein, its deletion mutant has no obvious phenotype, and BRS1 overexpression(OE) can restore the phenotype of BRI1 mutant. Compared with wild type, the OE lines own larger rosette leaf area, while the hypocotyl cells is obvious elongated. Plant height and fertility of the BR biosynthesis mutant det2-28 are obviously recovered after crossing with the BRS1 OE lines. Analysis of the expression levels of BRS1 in bri1-5 and det2-28 before and after BL treatment reveals that BRS1 is regulated by BR, and this regulation is dependent on the BR signaling pathway. After assay analysis of the Ws-2, bri1-5,bri1-5 brs1-1D found that BRS1 may influence the redox balance and probably relate to ethylene signaling.Previous studies have found that BR signaling can improve plant tolerance to pathogens and abiotic stress, BR signaling system is antagonistic with the innate immune system in plant. Thus,we want to study whether BRS1 will involve in this process. Firstly, we use flg22 to imitate innate immune response and aniline blue staining find that BRS1 overexpression can increase callose.This result confirms BRS1 involves plant innate immunity. Subsequently, by DAB straining we find that BRS1 overexpression increases the accumulation of ROS in the cell, and theaccumulation is alleviated after BL treatment. Overexpression of BRS1 increases the expression of defense related genes including ethylene responsive genes. Thus, BRS1 is involved in the BR-regulate stress response and likely related to the ethylene pathway.