Comparative transcriptome analysis between a resistant and a susceptible Chinese cabbage in response to Hyaloperonospora brassicae .

Downy mildew caused by Hyaloperonosporabrassicae (H. brassicae) leads to up to 90% of the crop yield loss in Chinese cabbage in China. A transcriptome analysis was carried out between a resistant line (13-13, R) and a susceptible line (15-14, S) of Chinese cabbage in response to H. brassicae. The NOISeq method was used to find differentially expressed genes (DEGs) between these two groups and GO and KEGG were carried out to find R genes related to downy mildew response of Chinese cabbage. qRT-PCR was carried out to verify the reliability of RNA-seq expression data. A total of 3,055 DEGs were screened out from 41,020 genes and clustered into 6 groups with distinct expression patterns. A total of 87 candidate DEGs were identified by functional annotation based on GO and KEGG analysis. These candidate genes are involved in plant-pathogen interaction pathway, among which 54 and 33 DEGs were categorized into plant-pathogen interaction proteins and transcription factors, respectively. Proteins encoded by these genes have been reported to play an important role in the pattern-triggered immunity (PTI) and effector-triggered immunity (ETI) processes of disease responses in some model plants, such as Arabidopsis, rice, tobacco, and tomato. However, little is known about the mechanisms of these genes in resistance to downy mildew in Chinese cabbage. Our findings are useful for further characterization of these candidate genes and helpful in breeding resistant strains.