为揭示植物抗旱的调控机理, 对复苏植物旋蒴苣苔(Boea hygrometrica)的一个编码C2结构域小蛋白的基因BhC2DP1进行研究。Real-time PCR和Pro_BhC2DP1:GUS报告基因检测显示, 该基因只在干旱早期和外源Ca²⁺处理0.5小时时受诱导表达; 分别施加Ca²⁺螯合剂EGTA和逆境激素ABA均抑制该基因表达, 但二者同时处理则显著诱导其表达, 表明ABA对该基因转录水平的调控是Ca²⁺依赖型的。过表达BhC2DP1的拟南芥(Arabidopsis thaliana)对ABA的敏感性增强, EGTA处理可消除其与野生型的差异, 表明Ca²⁺是BhC2DP1蛋白参与ABA反应所必需的。综上所述, ABA和Ca²⁺信号途径的精细调控可能是决定干旱诱导旋蒴苣苔中BhC2DP1基因表达时间、丰度和功能的重要机制。

Here we report on the cloning and characterization of BhC2DP1, a novel gene encoding a plant-specific small protein with a single C2 domain from the resurrection plant Boea hygrometrica. Phylogenic analysis of C2-domain proteins and sequence analysis revealed that BhC2DP1 belongs to the C2 elicitor responsive protein subfamily. Real-time PCR and histochemical study of a GUS reporter gene driven by the BhC2DP1 promoter in transgenic Arabidopsis showed BhC2DP1 transcripts increased at the early stage after dehydration and exposure to exogenous Ca²⁺ but decreased with prolonged treatment. Expression of BhC2DP1 was suppressed by abscisic acid (ABA) and Ca²⁺-chelating agent EGTA but was promoted by simultaneous exposure to ABA and EGTA, suggesting that the transcriptional regulation of BhC2DP1 by ABA is Ca²⁺ dependent. Constitutive overexpression of BhC2DP1 in Arabidopsis resulted in an ABA-hypersensitive phenotype, which was rescued by supplementing EGTA to growth media. Therefore, Ca²⁺ is necessary for the function of BhC2DP1 in responding to ABA. Our results provide new insights into the role of small C2-domain proteins and the fine-tuning regulation mechanism in response to drought stress.