中文摘要：

核桃（JuglansregiaL．）坚果是重要的天然维生素E源。在维生素E合成代谢中，2-甲基-6-叶绿基-1，4-苯醌甲基转移酶（MPBQMTase）催化2-甲基-6-植基-1，4-苯醌（MPBQ）向2，3-二甲基-5-植基-1，4-苯醌（DMPBQ）的合成，是1-生育酚和IX-生育酚生物合成过程中的关键酶。本研究以‘香玲’核桃开花后90d的胚组织为材料，利用RACE技术克隆了核桃MPBQMT的eDNA。序列分析表明，得到的cDNA全长1280bp，有1020bp的开放阅读框（ORF），编码340个氨基酸，将其命名为jrV＇rE3。序列同源性比较显示，jrVTE3基因与毛果杨MPBQ／MSBQ甲基转移酶基因以及蓖麻、葡萄、大豆的内膜包装蛋白基因有同源性较高；其ORF编码的多肽序列与橡胶、莴苣、毛果杨的MPBQ／MSBQ转移酶及葡萄、蓖麻的内膜包装蛋白有较高的同源性。prrE3编码的多肽序列中，有15个氨基酸可能为蛋白激酶磷酸化位点，多肽序列二级结构中有α-螺旋、无规则卷曲。在多肽序列中，有-个低成分复杂性区域和-个跨膜区段，还有-个第-类s-腺苷甲硫氮酸甲基转移酶（AdoMet—MTases，ClassI）的保守域，这些序列结构体现了甲基转移酶结构的特点。这些结果对进-步研究核桃坚果仁中维生素E的合成的调控机制及核桃品质的遗传改良具有参考意义。

英文摘要：

Walnut （Juglans regia L. ） is an important natural source of Vitamin E. In the pathway for tocopher- ol synthesis, 2 - methyl - 6 - phytyl - 1,4 - benzoquinone methyltransferase （ MPBQMTase）, which catalyzed methylation of 2- methyl -6- phytyl -1,4- benzoquinone （MPBQ）to yield 2,3- dimethy1-5- phytyl - 1,4 - benzoquinone （DMPBQ）, was one of the key enzymes in the biosynthesis of γ - tocopherol and α - to- copherol. In this study, the cDNA encoding MPBQMTase of walnut was isolated from mature embryos （90 d after blossom） of ＇Xiang Ling＇ cultivar by rapid amplification of cDNA ends. The cDNA sequence analysis showed that the cDNA was 1280 bp in length with an open reading frame of 1020 bp encoding a polypeptide of 340 amino acids, and the gene was designated as jrVTE3. Sequence alignment indicated that the jrVTE3 had high homology with both the genes encode inner envelope proteins of Ricinus communls, Vitis vinifera, Glycine max and the mp- bqmt/msbqmt gene of Populus trichocarpa. The homology comparison analysis of predicted polypeptide sequence ofjrVTE3 showed that the protein had high identity with MPBQ/MSBQ methyltransferase of Hevea brasiliensis, Lactuca sativa, Ricinus communis and the inner envelope proteins of Vitis vinifera and Ricinus communis. Within the polypeptide sequence of jrVTE3 ,15 amino acids were predicted as phosphorylation sites. In addition, many chain extendings, α- helixs and irregular coils were found in its secondary structure. Moreover, plexity region, a transmembrane segment and a AdoMet - MTases（ class I） conserved domain were a low - com- also detected within the polypeptide sequences. The above charactereristics of the polypeptide sequence was highly consistent with that of methyltransferase. The results may be helpful for further study on revealing the metabolism of the Vi- tamin E and genetic improvment of walnut.