Abstract
BackgroundBrassinosteroids (BRs) are a type of sterol plant hormone that play an important role in various biochemical and physiological reactions such as promoting cell growth, increasing biomass, and improving stress resistance.ResultsTo investigate the regulatory and molecular mechanism of BRs on the growth and development of tea plants (Camellia sinensis L.), changes in cell structure and gene expression levels of tea leaves treated with exogenous BRs were analyzed by electron microscopy and high-throughput Illumina RNA-Seq technology. The results showed that the number of starch granules in the chloroplasts and lipid globules increased and thylakoids expanded after BR treatment compared with the control. Transcriptome analysis showed that in the four BR treatments (CAA: BR treatment for 3 h, CAB: BR treatment for 9 h, CAC: BR treatment for 24 h, and CAD: BR treatment for 48 h), 3861 (1867 upregulated and 1994 downregulated), 5030 (2461 upregulated and 2569 downregulated), 1626 (815 upregulated and 811 downregulated), and 2050 (1004 upregulated and 1046 downregulated) differentially expressed genes were detected, respectively, compared with CAK (BR treatment for 0 h). Using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases, metabolic pathway enrichment analysis showed that the differentially expressed genes of CAA vs. CAK, CAB vs. CAK, CAC vs. CAK, and CAD vs. CAK significantly enriched the functional categories of signal transduction, cell cycle regulation, and starch, sucrose, and flavonoid biosynthesis and metabolism pathways. We also found that after spraying BR, the key genes for caffeine synthesis were downregulated. The results of qRT-PCR coincided with the findings of transcriptomic analysis.ConclusionsThe present study improved our understanding of the effects of BRs on the growth and development of tea leaves and laid the foundation for the in-depth analysis of signal transduction pathways of BRs in tea leaves.
Highlights
Brassinosteroids (BRs), known as the sixth category of plant hormones [1], are involved in various physiological and biochemical reactions, plant growth and development by promoting cell growth, increasing biomass, and improving stress resistance [2]
In rice seedlings grown under the conditions of low temperature, low sunlight, and high precipitation, when the roots were soaked in 0.01-mg/L BR solution, plant height, leaf number, leaf area, millet number, and root number, survival rate, and aboveground dry weight were higher than the control group [8]
Ultrastructure of leaf cells Electron microscopic observation showed that among the five treatments studied, the largest starch grains were found in the samples sprayed with BRs for 48 h, with lipid globules in the chloroplast (Fig. 1: E)
Summary
Brassinosteroids (BRs), known as the sixth category of plant hormones [1], are involved in various physiological and biochemical reactions, plant growth and development by promoting cell growth, increasing biomass, and improving stress resistance [2]. Drought, and saline-alkali stress, BRs act as buffer to stress conditions by regulating the intracellular physiological environment, promoting normal physiological and biochemical metabolism, and enhancing plant stress resistance [7]. In rice seedlings grown under the conditions of low temperature, low sunlight, and high precipitation, when the roots were soaked in 0.01-mg/L BR solution, plant height, leaf number, leaf area, millet number, and root number, survival rate, and aboveground dry weight were higher than the control group [8]. Brassinosteroids (BRs) are a type of sterol plant hormone that play an important role in various biochemical and physiological reactions such as promoting cell growth, increasing biomass, and improving stress resistance
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