Isolation, expression, and evolution analysis of the type 2C protein phosphatase gene BcABI1 involved in abiotic and biotic stress in Brassica campestris ssp. chinensis

Abstract

Type 2C protein phosphatase (PP2C) is an important component of protein phosphatases involved in various biological processes, such as plant growth and development, cell cycle regulation, signal transduction, and environmental stress response. ABI1 (ABA insensitive 1), a member of the PP2C gene family, is a negative regulator in abscisic acid (ABA) signal transduction possibly related to stress tolerance, but ABI1 in economical plants is poorly understood. In this study, BcABI1 was isolated from Chinese cabbage [Brassica campestris (syn. B. rapa) L. ssp. chinensis (L) Makino] and 23 other cruciferous plants. Phylogenetic analysis was conducted according to the gene sequence of AtABI1 in Arabidopsis. Three introns are present in ABI1 genes encoding 400–437 amino acids. Multiple alignment of the sequences of 24 ABI1 genes showed that the ABI1 homologous genes of cruciferous plants were highly conserved. Meanwhile, the Ka/Ks values were obtained from orthologous gene pairs between the At genome and other crucifer crop genomes, and results showed that the natural selective pressures on these genes were purifying selection. Subsequently, the structure and expression profiles of BcABI1 were examined under abiotic and biotic stresses. BcABI1 presented a constitutive expression pattern, participating in wound stress and NaCl stress responses, and also induced by biotic stress in Chinese cabbage inoculated with Botrytis cinerea and Sclerotinia sclerotiorum. A significant difference between the pathogenic ability of the two bacteria can be observed, and the S. sclerotiorum caused faster pathogenesis. These results could help to elucidate the function of BcABI1 in plant growth and stress response, and gain valuable insights into Chinese cabbage breeding for the improvement of multiple-stress-tolerance.