Abstract: 【Objective】Identification of ACA genes family from Brassica rapa, and  analysis of the commonness and characteristics of family genes, which provided data support for further revealing the evolutionary relationship of ACA family. At the same time, analysis of the expression of BraACAs after self-pollination under abiotic stress, which laid the foundation for further exploring how BraACAs as regulate calcium to perform some biological functions. 【Method】Based on Arabidopsis genome database, the ACA gene family of Brassica rapa was identified by homologous alignment. The molecular weight, theoretical isoelectric point and other physicochemical properties were predicted by online software Expasy. Using MEGA 5.0 software to construct phylogenetic tree. Using online software GSDS 2.0 to draw gene structure map. According to the family gene location information, chromosome mapping was carried out in TBtools. Using McscanX software to carry out the collinearity analysis of ACA family genes in Arabidopsis and Brassica rapa. Using online software PlantCARE to predict and analyze the promoter elements of BraACAs. The protein conserved domains were analyzed by online tools Pfam and MEME. The expression of BraACAs gene in different tissues, abiotic stress and self-pollination were detected by qRT-PCR. 【Result】A total of 18 ACA genes were systematically identified from Brassica rapa, which are distributed on 10 chromosomes. According to the phylogenetic tree, classified into four groups including 3, 4, 4 and 7 members. There are many light, abiotic stress and hormone response elements in the promoter of ACA family genes in Brassica rapa, according to promoter element analysis, which indicates that ACA family genes have potential biological function of resisting stress. According to the analysis of protein domains, most of the ACA gene family proteins in Brassica rapa have four functional domains unique to the ACA family, and 13 of them have N-terminal autoinhibitory domains. The results of qRT-PCR showed that BraACAs were mainly expressed in flowers and pods, and the expression of Bra002762 and Bra035649 genes were up-regulated under chill stress, suggesting that Bra002762 and Bra035649 have potential biological functions in response to chill stress; the expression of Bra031701 gene was up-regulated under salt stress, suggesting that Bra031701 has potential biological functions in response to salt stress. There were significant differences in the expression of Bra003276 and Bra024117 genes between self-pollination and cross-pollination, suggesting that Bra003276 and Bra024117 responded to the self-incompatibility of Brassica rapa. The subcellular localization of these five genes were all located in the plasma membrane to verify their function of balancing ion concentration on the membrane. 【Conclusion】BraACAs protein structures contain four highly conserved domains. The expression of BraACAs is specific in tissues, five ACA family gene members encode proteins located on the cell membrane, of which Bra0002762, Bra035649, Bra031701 were associated with chilling and salt stress response, and Bra003276 and Bra024117 were associated with self-incompatibility reaction.

Key words: ACA gene family, Ca²⁺-ATPase; chilling stress, salt stress; self-incompatibility; Brassica rapa