Comprehensive analysis of bZIP gene family and function of RcbZIP17 on Botrytis resistance in rose (Rosa chinensis)*

Rose is an important ornamental plant and a commercial source of natural fragrances and essential oils. However, gray mold is the most serious disease of rose during cultivation and post-harvest. In plants, the bZIP gene family is one of the important families of transcription factors that regulate many biological processes, including pathogen defense, light response, and stress signaling. Although there were reports that bZIPs play a key role in plant pathogen defense, there have been no comprehensive studies or functional analysis of the bZIP gene family in rose (Rosa sp.) yet. In this study, a genome-wide analysis of the bZIP family gene (RcbZIPs) in rose was carried out to investigate their phylogenetic relationships, gene structure, chromosome localizations, collinearity, and the function of RcbZIP17. In the rose genome, 48 RcbZIP genes were identified and divided into 11 subgroups by phylogenetic relationships. Moreover, gene structure analysis agreed with phylogenetic tree grouping. The RcbZIPs were unevenly distributed on all seven chromosomes. The gene duplication events indicated that segmental duplication of the entire genome may play a key role in gene duplication. A Ka/Ks analysis showed that they mainly underwent purifying selection with limited functional differentiation. Gene expression analysis showed that 16 RcbZIPs were significantly differential expressed by Botrytis cinerea infection. It is speculated that these RcbZIPs are candidate genes for regulating the response of rose to gray mold infection. According to virusinduced gene silencing (VIGS) and overexpression (OE) studies, RcbZIP17 was implicated in the resistance of rose to gray mold. This study provides useful information for further study on the function of the bZIP gene family in rose.