谷子PP2C基因家族的特性

PP2Cs (2C type protein phosphatases)是一种单体丝氨酸/苏氨酸蛋白磷酸酶，在真核生物中，PP2Cs在脱落酸(ABA)、茉莉酸(JA)、水杨酸(SA)等激素信号传导途径中起着重要的调控作用。本研究通过序列比对，从谷子基因组中筛选出80个PP2C候选基因，聚类分析将其分为12个亚族(A、B、C、D、E1、E2、F1、F2、G、H、I、J)。与拟南芥PP2C基因家族比对表明，A~I为2个物种共有的亚族，J亚族只存在于谷子基因组中，L亚族只存在于拟南芥中。将谷子A亚族的10个成员命名为SiPP2CA1-10。基因表达谱分析表明，A亚族基因不同程度受ABA、干旱、高盐、低温和低氮诱导表达，其中，SiPP2CA6、SiPP2CA8在5种处理下诱导表达量都高。对10个A亚族成员的启动子分析发现，在这些基因的启动子序列中含有多种参与逆境胁迫应答的顺式作用元件，其中，SiPP2CA5、SiPP2CA6、SiPP2CA7、SiPP2CA8的启动子中含有参与低氮胁迫响应的元件。进一步研究发现，SiPP2CA8主要在根部表达，且在低氮胁迫下一直有较高的表达水平。亚细胞定位结果显示SiPP2CA8定位在细胞膜、细胞质、细胞核中；双分子荧光互补试验(BiFC)结果表明，SiPP2CA8与一个ABA受体类似蛋白SiRCAR3(基因号Si018317m.g)在细胞膜、细胞质及细胞核上互作，表明SiPP2CA8在谷子中可能参与ABA信号传导过程。

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

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 SiPP2CA8mainly expressed in root, and its expression remained at high level under low nitrogen stress. Subcellular localization showed that SiPP2CA8 waslocalized 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.