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. 2016 May 17:4:e1991.
doi: 10.7717/peerj.1991. eCollection 2016.

Transcriptomic analysis reveals distinct resistant response by physcion and chrysophanol against cucumber powdery mildew

Yanping Li  1 , Shilin Tian  2 , Xiaojun Yang  1 , Xin Wang  1 , Yuhai Guo  1 , Hanwen Ni  1
Affiliations

Transcriptomic analysis reveals distinct resistant response by physcion and chrysophanol against cucumber powdery mildew

Yanping Li et al. PeerJ. .

Abstract

Physcion and chrysophanol induce defense responses against powdery mildew in cucumbers. The combination of these two compounds has synergistic interaction against the disease. We performed RNA-seq on cucumber leaf samples treated with physcion and chrysophanol alone and with their combination. We generated 17.6 Gb of high-quality sequencing data (∼2 Gb per sample) and catalogued the expressions profiles of 12,293 annotated cucumber genes in each sample. We identified numerous differentially expressed genes that exhibited distinct expression patterns among the three treatments. The gene expression patterns of the Chr and Phy treatments were more similar to each other than to the Phy × Chr treatment. The Phy × Chr treatment induced the highest number of differentially expressed genes. This dramatic transcriptional change after Phy × Chr treatment leaves reflects that physcion combined with chrysophanol treatment was most closely associated with induction of disease resistance. The analysis showed that the combination treatment caused expression changes of numerous defense-related genes. These genes have known or potential roles in structural, chemical and signaling defense responses and were enriched in functional gene categories potentially responsible for cucumber resistance. These results clearly demonstrated that disease resistance in cucumber leaves was significantly influenced by the combined physcion and chrysophanol treatment. Thus, physcion and chrysophanol are appealing candidates for further investigation of the gene expression and associated regulatory mechanisms related to the defense response.

Keywords: Cucumber; Gene expression; RNA-seq; Transcriptomic.

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Conflict of interest statement

The authors declare there are no competing interests.

Figures

Figure 1
Figure 1. The global transcriptome similarity and differences caused by physcion and chrysophanol treatment for cucumber powdery mildew.
(A) Histological investigation of leaves inoculated with S. fuliginea at 3 dpi and 5 dpi after the four treatments. (B) Hierarchical clustering and heat map matrix of pairwise Pearson’s correlations of the expression profiles in leaves between the four treatments (solvent-treated control; chrysophanol treatment; physcion treatment; physcion and chrysophanol combination treatment) (log2-fold changes). (C) The up- and down-regulated DEGs. (D) A Venn diagram displaying the distribution of the DEGs.
Figure 2
Figure 2. Top 10 Go (gene ontology) and pathway categories enriched for up- (up arrows) and down-regulated (down arrows) genes differentially expressed in cucumber leaves activated by chrysophanol and/or physcion.
The p value, indicating the significance of the comparison, was calculated using a Benjamini-corrected modified Fisher’s exact test. BP, biological process; MF, molecular function.
Figure 3
Figure 3. Comparison of the proportions of defense-related genes in Chr1, Phy1 and Phy × Chr vs. Con1.
A bar left of the line means that the gene is down-regulated, while a bar right of the line means up-regulated.
See this image and copyright information in PMC

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Grants and funding

This work was supported by a grant from the National Natural Science Foundation of China (30971955). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.