Transcriptomic analysis identifies critical signaling components involved in the self-incompatibility response in Chinese cabbage

Abstract

Self-incompatibility (SI) is a genetic mechanism in plants to prevent inbreeding, promote outcrossing and thereby increase genetic diversity. Although current studies have well revealed the pathway of SI recognition specificity underlying interaction of female and male determinants in Brassica, the inhibition mechanism of incompatible pollen germination and tube growth is still deficient. In this study, histological analysis showed that the pollen germination and tube growth were obviously suppressed after self-pollination in self-incompatible Chinese cabbage. Furthermore, RNA-seq and gene expression analysis were performed to identify the differentially expressed genes (DEGs) involved in SI response of Chinese cabbage. A total of 59 DEGs belonging to known SI signaling factors and Ca2+-binding proteins were identified in Chinese cabbage after incompatible self-pollination. QRT-PCR analysis found that several genes were significantly differentially expressed during SI response. Chromosomal localization and potential duplicated genes were also predicted. Additionally, spatial-temporal expression profiling revealed that 15 DEGs were specifically expressed in the floral organ, some of which exhibited higher expressions in the anther and style. These findings will provide insights into the functional exploration of SI signaling factors in Chinese cabbage, and promote the further understanding of SI signaling networks in Brassica.