Screening and Functional Verification of Vernalization-Related Genes in Chinese Cabbage

Abstract

Flowering is very important for leaf head formation and breeding. Investigating the key genes related to vernalization process can reveal the flowering regulation mechanism and guide production and germplasm breeding. In this study, two Chinese cabbage (Brassica rapa subsp. pekinensis) inbred lines ‘1#’ and ‘2#’ with different winterness were used to identify vernalization-related genes. After low-temperature treatment, the transcriptomes of the shoot apex of the two lines were analyzed. The Arabidopsis thaliana homologues of 2,932 common differentially expressed genes with the same change trend after vernalization of two inbred lines were analysed based on Gene Ontology annotation and description. The results showed that, three genes were identified that may be related to the vernalization: Bra031210, Bra009126 and Bra033615. In which Bra031210 and Bra009126 were cloned, named BrGRP7.1 and BrCPD1, with open reading frames lengths of 507 and 1443 bp, encoding 168 and 480 amino acids, respectively. Through the expression patterns analysis, the expression of BrGRP7.1 showed a trend of initial decreasing (dipping at stage 1) and then increasing (peaking at stage 5) during flower bud differentiation of both inbred lines. Incontrast, BrCPD1 showed a first decreasing, then increasing, and last decreasing trend during flower bud differentiation of both lines. These two genes were transferred into wild-type A. thaliana. The flowering time of T2 generation of BrGRP7.1- and BrCPD1-transgenic plants was 2.31~5.11 days and 2.64~4.35 days earlier than the wild-type, respectively. In conclusion, this study screened three genes that involved in the vernalization process. Through functional verification, BrGRP7.1 and BrCPD1 were proved to have the ability to promote flowering time. This study provided a reference for further study on the flowering mechanism of Chinese cabbage.