IP3及其受体IP3Rs是钙信号转导通路的重要组成，是动物细胞维持正常生命活动不可或缺的部分。充足证据表明IP3在植物细胞感受非生物或生物胁迫及激素刺激引起胞质钙增加通路中也起着同样重要的第二信使作用。然而，植物IP3R一直是未解之谜。本课题组利用敲除STIM1后丧失SOCE的HEK293细胞系，采用功能克隆方法从拟南芥cDNA文库获得了一个能够重新引起胞质钙增加的功能未知基因。初步研究发现其为IP3结合蛋白，且极有可能是IP3R：1）该基因突变可导致拟南芥根细胞ABA引起胞质钙增加的缺失及拟南芥生长发育对ABA的不敏感；2）利用微量热涌动技术证明该基因编码蛋白能够特异结合IP3，Kd值为311 nM。据此，拟利用生化、分子、遗传及细胞生物学等技术方法详细探索该IP3结合蛋白结合IP3生化特性，介导ABA引起胞质钙增加作用机理及其生物学功能，为其是否为植物IP3受体提供更多证据。

IP3 and its receptors (IP3Rs) are the important component of calcium signal transduction pathways and the indispensable part for maintaining normal animal activities. Previous solid studies showed that IP3 is also an essential secondary messenger for sensing various extracellular biotic or abiotic stresses and intracellular hormone stimulus to induce intracellular calcium increases in plants. However, the plant IP3R is still unclear. My group have used a functional screening assay in HEK 293 cells which lost the store-operated calcium entry (SOCE) by knocked-outing STIM1 to isolate an Arabidopsis complementary DNA clone encoding an IP3 binding protein (IP3BP). We proposed a hypothesis: This IP3BP could be a first plant IP3R, because we found that ABA-induced cytosolic [Ca2+] increase was impaired in the ip3bp plant compared with the Arabidopsis wildtype (WT), and the growth and development of ip3bp plant is less sensitive to ABA than that of WT. In addition, this IP3BP specifically bind IP3 in vitro with the Kd of 311 nM. So, in this project, we will perform different methods and techniques in biochemistry, molecular biology, genetics, and cell biology to comprehensively characterize the IP3-bind activity, the mechanism on ABA-induced cytosolic [Ca2+] increase, and the physiological function of this IP3BP in Arabidopsis and give more scientific evidences to confirm this IP3BP is a plant IP3R.