Genome-Wide Gene Expression Profiles of Orange and White Leafy Head Chinese Cabbage (Brassica rapa L. ssp. pekinensis) during the Summer Production Season

Abstract

The orange color of the inner leaves of Chinese cabbage (Brassica rapa L. ssp. pekinensis) is attributed to the high content of carotenoids, which is controlled by a single recessive gene, BrCRTISO (Br-or). Due to the important roles of carotenoids in human, the orange color of inner leaves is a desirable agronomic trait for Chinese cabbage breeding. However, Chinese cabbages with orange inner leaves are more susceptive to plant disease and insect pests. To understand the molecular mechanisms of abnormal carotenoid metabolism of B. rapa during the summer production season, we employed RNA-seq to analyze the differentially expressed genes between the F2 populations of an orange Chinese cabbage cultivar (14-490) and a white Chinese cabbage cultivar (14-401). A total of 30 768 genes were detected, among which, 175 genes, including 44 up-regulated genes and 131 down-regulated genes, were differentially expressed between the orange and white F2 populations. Genes involved in cold response, wounding response, salt stress, defense response and drought stress were highlighted. In addition, other genes encoding transcription factors were also identified, including heat shock protein 70, WRKY70 and MYB34. Our study provides new insight into the regulatory network of gene expression in orange head Chinese cabbage during the summer production season. These response genes may be used for further strategy development of Chinese cabbage cultivars with high carotenoid content in summer planting.