中文摘要：

生殖隔离在形成新物种和物种同一性的保持中有重要作用,因而在水稻优化育种中有重要的意义.S5位点是一个已克隆的控制水稻生殖隔离的基因,它产生的S5-ORF3,ORF4和ORF5蛋白质共同调控着indica-japonica杂交后代的育性,特别是S5-ORF3蛋白质在打破水稻亚种indica-japonica之间的生殖隔离与促进物种间的基因交流中发挥重要作用.针对S5-ORF3的进化分析对于研究它的功能和起源很重要,但目前尚无报道.本文基于序列和进化分析,提出S5ORF3为一种定位在内质网中的新的HSP70家族蛋白,但缺乏HSP70的C端的多肽结合结构域,推测S5-ORF3可能通过影响alpha淀粉酶的合成来作用于内质网压力;找到了ORF3的19条同源蛋白,并用极大似然算法构建了可靠的进化树,发现水稻的S5-ORF3与节节麦的luminal-binding蛋白进化关系最为密切;作了置信度100％的S5-ORF3蛋白质的三维结构预测,预测了居中的配体绑定位点;发现了水稻的S5-ORF3与其他HSP70蛋白相比独特的基序,为进一步研究S5-ORF3的作用机理和演化历史提供了线索和数据支持.

英文摘要：

Reproductive isolation is important in speciation and maintaining species identity,so it is very significant in optimization of breeding rice.S5-locus is a cloned gene controlling the reproductive isolation,which produces proteins S5-ORF3,ORF4and ORF5 that work together to regulate fertility in indica japonica hybrids,and especially the S5-ORF3 protein plays a very important role in distorting reproductive isolation among indica japonica and enhancing gene flow among populations.The evolutionary analysis of S5-ORF3 is significant for studying its function and origin,which is still no reported.In this paper,based on sequence and evolution analysis,it is proposed that the S5-ORF3 is a new HSP70 family protein which is located in endoplasmic reticulum （ER） and lacks of multi-peptide binding domain.Evolution analysis suggests that S5-ORF3 might act on ER stress via affecting alpha amylase synthesis; moreover,19 homologous proteins of S5-ORF3 are found,ML phylogenetic tree is constructed,and it is found that there is close evolution relationship between rice S5-ORF3 and a luminal binding protein of Aegilops tauschii; the 3D structure of S5-ORF3 with confidence of 100％％ is predicted,as well as a ligand binding site located in the middle of S5ORF3.The specific motif of rice S5-ORF3 among HSP70 family is also found.This work may provide some clues and data for studying function and evolution history of rice S5-ORF3.