Abstract:

Auxin （IAA） signaling pathway plays an important role in plant growth and response to biological and abiotic stress. Powdery mildew （PM） is a common and serious disease in pumpkin. In order to explore the molecular mechanism of IAA signaling pathway in response to PM stress， transcriptomic sequencing and whole genome DNA methylation sequencing were performed on pumpkin leaves treated with PM. As a result， we found 25 differentially expressed genes in the IAA signaling pathway. Fifty-three genes were differentially methylated， among which 16 austerin-upregulated small RNA （SAUR） genes were methylated to different degrees， suggesting that these genes may be involved in the response to powdery mildew stress. The methylation level of SAUR50 （CmoCh19G007170） gene was reduced， and the methylation region was located in the promoter region of the gene. The expression level of SAUR50 was significantly up-regulated under PM stress and significantly down-regulated under IAA induction. Therefore， this gene may regulate its expression level through DNA methylation and participate in the regulation of PM stress in pumpkin through IAA signaling pathway. The results provided a theoretical basis for IAA signaling pathway in response to powdery mildew stress molecular breeding of pumpkin resistant to PM.

Key words: powdery mildew, auxin signaling pathway, DNA methylation, transcriptome

摘要：

生长素（auxin, IAA）信号途径在植物生长、生物胁迫和非生物胁迫响应中发挥着重要的作用。白粉病是南瓜普遍发生且较为严重的一种病害，为探究IAA信号途径响应白粉病胁迫的分子机制，对白粉菌处理的南瓜叶片进行了转录组测序和全基因组DNA甲基化测序分析。结果发现，在IAA信号途径中，有25个差异表达基因，53个基因发生了差异甲基化，其中16个生长素上调小RNA (SAUR)基因均发生了不同程度的甲基化，说明这些基因可能参与了白粉病胁迫响应。SAUR50（CmoCh19G007170）基因的甲基化水平降低，且甲基化区域位于基因的启动子区。在白粉病胁迫下SAUR50的表达水平显著上调，在IAA诱导下显著下调，因此该基因可能通过DNA甲基化调节其表达水平，并且通过IAA信号途径参与南瓜白粉病胁迫的调控。研究结果为IAA信号途径响应白粉病胁迫途径与抗白粉病南瓜分子育种提供了理论依据。

关键词: 白粉病, 生长素信号途径, DNA甲基化, 转录组