Characteristics of PP2C Gene Family in Foxtail Millet ( Setaria italica )

Abstract

PP2Cs are a group of monomeric serine/threonine protein phosphatases, which play an important role in regulation of hormone signaling pathways such as abscisic acid(ABA), jasmonic acid(JA) and salicylic acid(SA) in eukaryotes. In this study,we identified 80 candidate PP2C genes from foxtail millet genome via sequence alignment, and cluster analysis showed that PP2Cs in foxtail millet were divided into 12 subfamilies(subfamily A, B, C, D, E1, E2, F1, F2, G, H, I, and J). Foxtail millet and Arabidopsis share A, B, C, D, E1, E2, F1, F2, G, H, and I, while subfamily J is only in foxtail millet and subfamily L is only in Arabidopsis. Ten members of subfamily A in foxtail millet were named as SiPP2CA1–10, and gene expression profiles showed that the expression of these genes was induced by ABA, drought, high salt, cold and low nitrogen stresses. Among them,SiPP2CA6 and SiPP2CA8 showed high expression level in all treatments. Promoter analysis identified a variety of cis-acting elements involved in stress responses in promoter region of members in subfamily A, and a specific element responding to low nitrogen stress in SiPP2CA5, SiPP2CA6, SiPP2CA7, and SiPP2CA8. Further study demonstrated that SiPP2CA8 mainly expressed in root, and its expression remained at high level under low nitrogen stress. Subcellular localization showed that SiPP2CA8 was localized in cytomembrane, cytoplasm and nucleus. Bimolecular fluorescence complementation(BiFC) assay demonstrated that SiPP2CA8 interacted with an ABA receptor like protein, SiRCAR3(gene locus Si018317m.g), in cytomembrane, cytoplasm and nucleus. These results suggested that SiPP2CA8 may participate in ABA signaling pathway in foxtail millet.