Abstract
Brassinosteroid (BR), a kind of polyhydroxylated steroid hormone, plays an important role in physiological and biochemical processes in plants. Studies were mainly focused on BR signaling and its exogenous spraying to help enhance crop yields. Few research studies are centered on the accumulation pattern of BR and its mechanism. Yet, it is crucial to unlock the mystery of the function of BR and its cross action with other hormones. Tea (Camellia sinensis (L.) O. Kuntze) is one of the important economic crops in some countries, and new shoots are the raw materials for the preparation of various tea products. Different concentrations of exogenous BR were reported to have different effects on growth and development. New shoots of tea plants can thus be considered a valuable research object to study the accumulation pattern of BR. In this study, the quantity of five BR components (brassinolide, 28-norbrassinolide, 28-homobrassinolide, castasterone, and 28-norcastasterone) in different tissues of tea plants, including buds (Bud), different maturity of leaves (L1, L2), and stems (S1, S2) were determined by UPLC-MS/MS. A total of 15 cDNA libraries of the same tissue with three repetitions for each were constructed and sequenced. The BR-accumulation pattern and gene expression pattern were combined together for weighted gene co-expression network analysis (WGCNA). BR-accumulation-relative genes were then screened using two methods, based on the K.in value and BR biosynthetic pathway (ko00905), respectively. The result showed that photosynthesis-related genes and CYP450 family genes were actively involved and might play important roles in BR accumulation and/or its accumulation pattern. First and foremost, feedback inhibition was more likely to dominate the accumulation pattern of BR in the new shoots of tea plants. Moreover, three conserved miRNAs with their target transcriptional factors and target mRNAs had been figured out from negative correlation modules that might be strongly linked to the BR-accumulation pattern. Our study provided an experimental basis for the role of BR in tea plants. The excavation of genes related to the accumulation pattern of BR provided the possibility of cross-action studies on the regulation of BR biosynthesis and the study between BR and other hormones.
Highlights
Brassinosteroid (BR), known as the sixth natural phytohormone, is a polyhydroxylated steroid hormone (Liu L. et al, 2021)
The contents of five main substances of BR biosynthetic metabolites (Supplementary Table S1), BL, 28-norBL, 28homoBL, CS, and 28-norCS had been detected in the new shoots of tea plants via UPLC-MS/MS
The results showed that the contents of CS in Bud, L1, L2, S1, and S2 were 1.63, 1.71, 2.54, 1.50, and 0.97, respectively
Summary
Brassinosteroid (BR), known as the sixth natural phytohormone, is a polyhydroxylated steroid hormone (Liu L. et al, 2021). BR promotes cell elongation, cell division (Que et al, 2018; Oh et al., 2020; Conway et al, 2021), seed germination (Zhong et al, 2021), and fruit ripening (He et al, 2018) during growth and development, and it plays an important regulatory role in plants under stress (Farooq et al, 2009; Procházka et al, 2016; Soares et al, 2020). A proven strategy to know how BR works is to figure out the biosynthesis pathway of BR in plants. There are three main forms of BR in plants: C27-BR, C28-BR, and. Catalytic enzymes and biosynthetic genes have been excavated through the C28-BR biosynthetic pathway (Figure 1A), and it has been well understood. The C28-BR biosynthesis pathway starts from campesterol (CR), a biosynthetic substrate, and can be carried out through two parallel pathways, which are campestanol (CN)-
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