水稻乙烯受体类似物基因的克隆及其表达特性

乙烯在植物的生长发育以及对逆境的反应中起着重要作用。乙烯受体基因在拟南芥、烟草和番茄等双子叶植物中已有一些研究,但到目前为止还没有见到关于单子叶植物乙烯受体研究的报道。我们从水稻中克隆了一个乙烯受体基因OSPK2,发现它所编码的蛋白与双子叶植物的乙烯受体有所不同。OSPK2的N端较长,其后是3个跨膜区、一个GAF结构域、一个推测的激酶结构域和接受器结构域。虽然大多数的结构域都是保守的,但预期的磷酸化位点His和磷酸基团接受位点Asp在OSPK2中分别被Gln和Asn取代。这一事实说明,OSPK2可能不是以组氨酸激酶的磷酸转移方式进行作用,而是以其他的机制,如具有丝/苏激酶的活性。应用RT-PCR方法对不同条件下OSPK2基因的表达进行了研究,结果表明,OSPK2受伤害和PEG处理诱导,但盐及ABA处理对其没有显著影响。OSPK2基因的差异表达可能反映了它在介导不同非生物逆境反应中的作用,这与我们以前关于烟草乙烯受体的研究结果是一致的。

Cloning of the Full-length Gene for Tobacco Ethylene Receptor NTHK2 and Characterization of Its Kinase Domain

Previously the partial sequence of an ethylene receptor gene NTHK2 was isolated from tobacco (Nicotiana tabacum L. var. Xanthi) plants and it was wound and drought inducible. In the present study full-length cDNA of NTHK2 was cloned by 5'-RACE method. NTHK2 gene has 3 216 bp, with 509 bp of 5'-non-coding region and 427 lip of 3'-non-coding region, and encodes an ethylene-receptor homolog of 760, amino acids. NTHK2 protein has a putative signal peptide, three transmembrane domains, a histidine kinase domain and a receiver domain. In the putative histidine kinase domain, the histidine at the phosphorylation site was replaced by an asparagine. To study the biochemical property of NTHK2, its kinase domain was expressed as a fusion protein with glutathione S-transferase (GST) using yeast Schizzosaccharomyces pombe as an expression system. In vitro kinase assay showed that NTHK2 kinase domain can autophosphorylate in the presence of Mg2+, indicating that NTHK2 may function as a kinase. Further studies will elucidate the function of NTHK2 in plant.