Comparative Transcriptome Analysis of Two Contrasting Chinese Cabbage ( Brassica rapa L.) Genotypes Reveals that Some Kinds of Phytohormones Accumulation Involved in the Local Bulges Formation on the Leaf Surface

The presence of crinkly (local bulges) on the leaf surface of Chinese cabbage is a typical characteristic to distinguish different Chinese cabbage cultivars. Previously, the studies on leaf development regulation genes are mostly focused on model plants. However, the studies on crinkly leaves of Chinese cabbage are relatively lagging. To understand the mechanisms of local bulges formation, two leaf surfaces with significant difference inbred lines T599 and Y317 were used. The content of multiple phytohormones and the differentially expressed genes among the crinkly and flat leaves of T599 (T599C and T599F) and the flat leaves of Y317 (Y317F) were analyzed using RNA-seq method. The results showed that the content of IAA, TZR, Zeatin, IPA, GA1 and GA3 were higher in crinkly leaves than that in flat leaves. Through RNA-seq, total 1.708 DEGs and 4.791 DEGs were identified from T599C vs. T599F and T599C vs. Y317F, respectively, and among them, 488 common DEGs with similar expression trend between crinkly and flat leaves were further identified. Additionally, analysis of the common DEGs expression pattern suggests transcription factors, plant hormones biosynthesis and signal transduction, plant growth and development, and cell wall biosynthesis and degradation might play a critical role in regulating the crinkly formation on the leaf surface of Chinese cabbage. Our study provides new insight into phytohormones and the regulatory network of gene expression in the crinkly leaves and flat leaves of Chinese cabbage. These response genes may be used for further strategy development of Chinese cabbage cultivars with leaf flatness.