Genome wide analysis of BnAPs gene family in <italic>Brassica napus</italic>

Abstract

<p id="C3">Aspartate protease (AP) is one of the four major proteolytic enzymes and plays an important role in protein processing, signal transduction, and stress response. <italic>Brassica napus</italic> is an important oil crop in China. We identified 154 APs coding genes in <italic>Brassica napu</italic> by protein homology analysis, which encoded typical, atypical, and nucellar aspartate proteases, respectively. Gene structure analysis showed that most <italic>BnAPs</italic> genes contained 1-4 exons and the motif distribution of the same type of aspartic protease was similar. Collinearity analysis revealed that there was a large number of homologous genes between <italic>Brassica napus</italic> and <italic>Brassica rape</italic>, <italic>Brassica oleracea</italic> and <italic>Arabidopsis thaliana</italic>, and about 89% of <italic>BnAPs</italic> genes came from genome-wide replication events. Transcriptional analysis demonstrated that <italic>BnAPs</italic> gene family was expressed in all tissues. The stigma of <italic>BnAP30.A05.1/ A05.2/C05.1/C05.2</italic>, <italic>BnAP36.A04/C08</italic>, and <italic>BnAP39.A06/C03</italic> increased significantly after pollination. <italic>Cis</italic>-element analysis in the promoter region of <italic>BnAPs</italic> gene presented that stress-related cis regulatory elements were significantly enriched. We further verify that the relative expression levels of these genes rich in stress-related cis regulatory elements changed significantly after stress (ABA, NaCl, or 4℃), suggesting that these <italic>BnAPs</italic> genes may be involved in response to stress in <italic>Brassica napus</italic>. Compared with <italic>Arabidopsis </italic>homologous genes, about 24% of <italic>BnAPs</italic> had the same expression pattern as their homologous <italic>AtAPs.</italic> This study laid a foundation for further understanding the biological function of aspartic protease family in <italic>Brassica napus</italic>.