桑树光合系统ⅡMPsbR基因的克隆及在不同部位表达分析

Cloning of Photosystem ⅡMPsbR Gene and Its Expression Analysis in Different Parts of Morus L.

根据桑树表达序列标签(ESTs),采取RT-PCR方法克隆了一个编码桑树光合系统ⅡPsbR基因的全长cDNA序列,以期为从分子水平上揭示桑树高效光合作用的机制奠定基础。序列分析表明,该基因全长623 bp,存在56 bp的5’-UTR和306 bp的3’-UTR,其开放阅读框(ORF)长261 bp,编码86个氨基酸,预测蛋白质分子质量为8.95 kD,等电点为11.09。同源分析表明,桑树光合系统ⅡMPsbR基因与花生、大豆编码氨基酸具有较高的同源性;根据MPsbR基因的氨基酸序列与其他20个物种的氨基酸同源序列构建的系统进化树表明,桑树与花生、海桑、梨、大豆的亲缘关系较近。半定量RT-PCR研究表明,桑树光合系统MPsbR基因在桑树不同部位的表达水平有一定差异,在幼叶(刚展开第一张叶)和顶芽表达量最高,其作用机理有待于进一步研究之中。

Based on the expression sequence label（ESTs）,the full length cDNA sequence coding for photosynthesis system ⅡPsbR in Morus L.was cloned by RT-PCR,and named MPsbR（Genbank accession number： GU937873）.The sequential analysis indicated that the length of the gene was 623 bp,and contains 56 bp 5＇-UTR and 306 bp 3＇-UTR.The length of its opening reading frame（ORF） was 261 bp encoding 86 amino acids with apredicted molecular weight of 8.95 KD and an isoelectric point of 11.09.Homology analysis revealed that MPsbR gene are highly conservative in Morus L.and other species including Arachis hypogaea and Glycine max;The phylogenetic analysis based on MPsbR gene with other 20 species indicated that Morus L.shows closer relationship with Arachis hypogaea,Sonneratia caseolaris,Pyrus pyrifolia and Glycine max.The results of semi quantitative RT-PCR analysis showed that the transcriptional level of MPsbR mRNA in the young leaf and the top bud were the highest.Its action mechanism was waiting for further studies.