Transcriptome Analysis on Asymmetric Root Growth of Oryza sativa Induced by Brassinosteroids via Ethylene Pathway

The growth of plant roots is regulated by various factors. Brassinosteroids (BRs) can induce asymmetric root growth (ARG) to form waves and coils, and this phenomenon can be eliminated by ethylene (ETH) inhibitors aminoacetic acid (AOA) or silver thiosulfate (STS), indicating this process depends on ETH pathway. Nevertheless, the research on related genes has not been reported. In this study, four treatments (Water, Brassinolide (BL), BL + AOA, and BL + STS) were set up using the seedlings of Oryza sativa as materials. The differentially expressed genes (DEGs) in BR-induced ARG via ETH pathway were identified by transcriptome sequencing, weighted gene co-expression network analysis (WGCNA), and real-time quantitative PCR (qRT-PCR). Finally, we screened 70 DEGs, including ALPHA-EXPANSINs (OsEXPAs), WALL-ASSOCIATED RECEPTOR KINASE-LIKE 16 (OsWAKL16), and TRANSMEMBRANE KINASE (OsTMK) that regulated cell elongation and expansion, as well as plant hormone synthase genes, 1-AMINO-CYCLOPROPANE-1-CARBOXYLIC ACID OXIDASEs (OsACOs), OsYUCCAs, and CYTOKININ OXIDASE(OsCKX). Most of them were up-regulated by BRs via ETH pathway. In addition, the receptor-like kinase (RLK) gene ROOT MEADNDER CURLING (OsRMC), a negative regulator in jasmonic acid-induced ARG, could be inhibited by BRs, and this process also depended on ETH pathway. The identification of the above genes provides evidence for revealing the molecular mechanism in the process.