Transcriptome analysis of asymmetric root growth of O. sativa induced by ambient temperature through ethylene pathway

Plant roots can sense external stimuli and make morphological changes. Under certain conditions, roots will grow asymmetrically to adapt to environmental changes. Ambient temperature (AT) and plant hormones have important effects on the growth of plant roots. Although it has been known that ethylene (ETH) was a key node regulating asymmetric root growth (ARG), the effect of AT on ARG was still unknown. Meanwhile, the relationship between AT, ETH, and ARG was also unclear. Here, we used O. sativa seedlings as material, and found that higher AT could induce ARG of O. sativa, which depended on ETH pathway. The results showed that AT-induced ARG depended on ETH synthesis and signal transduction, and the related genes were OsACOs and OsERFs. In the downstream of ETH, on one hand, there were significant differences in the expression of some genes related to auxin polar transport, signal transduction and synthesis, such as OsABCB15, OsNPFs, OsYUCCA5; On the other hand, the expression of genes regulated root elongation changed significantly, such as OsEXPA6, OsXTR8, OsCYCD3 and so on. In addition, there were significant differences in the expression of receptor like kinase (RLK) gene OsRMC, which inhibited ARG of O. sativa. The above DEGs were up-regulated in 35 degrees treatment and down regulated in inhibitor treatment. In conclusion, this study found for the first time that high AT can induce ARG through ETH pathway, and provided a basis for revealing the molecular mechanism of ARG induced by AT through ETH pathway.

植物根系能够感知外界刺激并发生形态学改变。在特定条件下，根系会通过不对称生长以适应环境变化。环境温度（Ambient temperature, AT）与植物激素对植物根系生长具有重要调控作用。尽管已有研究表明乙烯（ethylene, ETH）是调控根系不对称生长（asymmetric root growth, ARG）的关键节点，但环境温度对ARG的调控效应仍未明确，且AT、ETH与ARG三者间的相互关联也尚未阐明。本研究以水稻（Oryza sativa, O. sativa）幼苗为实验材料，发现较高的环境温度可诱导水稻产生ARG，且该过程依赖于ETH信号通路。实验结果显示，AT诱导的ARG依赖于ETH的合成与信号转导，相关调控基因为OsACOs与OsERFs。在ETH信号通路的下游，一方面，部分参与生长素极性运输、信号转导及生物合成的基因表达量出现显著差异，例如OsABCB15、OsNPFs、OsYUCCA5；另一方面，调控根系伸长的基因表达也发生显著改变，如OsEXPA6、OsXTR8、OsCYCD3等。此外，类受体激酶（receptor like kinase, RLK）基因OsRMC的表达量存在显著差异，该基因可抑制水稻的ARG。上述差异表达基因（differentially expressed genes, DEGs）在35℃处理组中呈上调表达，在抑制剂处理组中呈下调表达。综上，本研究首次发现高温可通过ETH信号通路诱导水稻ARG，为阐明AT通过ETH通路调控ARG的分子机制提供了实验依据。