关键词: 谷子, 脱落酸, 禾生指梗霉, PYL, SnRK2, 加权基因共表达网络

Abstract:

【Objective】Abscisic acid (ABA), as a stress hormone, plays an important role in plant growth and development, biological and abiotic stresses. The ABA receptor protein PYR/PYL/PCAR and SNF1-related protein kinase (SnRK2) are important regulatory factors that mediate ABA signaling. The objective of this study is to predict the regulatory roles of ABA and the key genes in its signaling pathway in foxtail millet (Setaria italica) downy mildew caused by Sclerospora graminicola, and to provide a reference for the research of endogenous ABA in S. italica in response to the infection of S. graminicola.【Method】S. italica variety Jingu 21 infected by S. graminicola was used for transcriptome sequencing and ABA content measurement, and the PYL and SnRK2 family genes in the ABA signaling pathway were identified and analyzed based on the whole genome sequence of S. italica. A weighted gene co-expression network analysis (WGCNA) was constructed using the transcriptome, and it was associated with the content of host endogenous ABA in the context of S. graminicola infection to predict the key genes in the interaction between S. italica and S. graminicola regulated by ABA and the PYL and SnRK2 genes in its downstream signaling. The candidate genes were validated by qRT-PCR.【Result】There were 11 PYL and 11 SnRK2 family genes in S. italica, which were relatively conservative in the Gramineae, and ABA responsive elements were predicted in the promoters of PYL and SnRK2 family genes. The endogenous ABA in the host accumulated at the first and second stages after S. graminicola infection, and its content (22.50 and 18.08 ng·mL^-1, respectively) was significantly higher than that of the control group. However, the content of ABA decreased at the third, fourth, and fifth stages, which was lower than that of the control group. For the WGCNA, a total of 34 gene co-expression modules were constructed by using 18 535 genes. The MEpaleturquoise and MEbrown modules were predicted as the core candidate modules through the association analysis of ABA content and PYL, SnRK2 family genes. GO function enrichment and module key gene mining revealed that one PYL family gene (Seita.1G030500), two SnRK2 family genes (Seita.2G394500 and Seita.3G03200), and three core genes (Seita.4G105600, Seita.6G218100, and Seita.9G138400) might be involved in the interaction between S. italica and S. graminicola during the regulation of ABA and its signal transduction. After comparing three predicted core genes with the reference genes in Oryza sativa and Arabidopsis thaliana databases, Seita.4G105600 was identified as the transducin/WD40 repeat-like superfamily protein, Seita.6G218100 as the WRKY57 transcription factor, and Seita.9G138400 as the TIFY transcription factor. qRT-PCR analysis showed that Seita.2G394500, Seita.4G105600, and Seita.6G218100 genes were up-regulated at the early stage of S. graminicola infection.【Conclusion】The ABA accumulates in S. italica infected by S. graminicola. One PYL family gene, two SnRK2 family genes, two transcription factor genes, and one WD40 family protein gene were predicted as the key genes related to the response to S. graminicola infection. qRT-PCR results showed that one SnRK2 gene, one WD40 family protein gene, and one WRKY57 transcription factor gene may play an important role in the response of ABA in S. italica to the infection of S. graminicola.

Key words: foxtail millet (Setaria italica), abscisic acid, Sclerospora graminicola, PYL, SnRK2, weighted gene co-expression network analysis (WGCNA)