甜瓜抗霜霉病基因同源序列克隆与分析

采用RT—PCR扩增的方法，从高抗霜霉病甜瓜品种‘日本安农二号’中克隆到约3kb的cDNA片段（命名为MRGH-D，该基因是一个连续的通读编码框，编码1007个氨基酸。推测的蛋白质分子量为113．7kDa，等电点为7．88，蛋白质预测无跨膜区。根据推测的氨基酸序列，该基因属于TIR—NBS—LRR类抗病基因，具有TIR-NBS—LRR类抗病基因所有的保守结构域。核苷酸序列和氨基酸序列同源性分析结果显示，MRGH-J与甜瓜抗病基因的同源序列MRGHl2及抗霜霉病相关基因mp-19均具有高达99％的同源性，推测该基因可能在甜瓜抗霜霉病中起作用。

Cloning and Sequence Analysis of Resistance to Downy Mildew Gene Analogs from Melon (Cucumis melon L.)

The cDNA sequence (named MRHG-j) which was 3 kb long and encoded 1 007 amino acids was cloned from the melon of high resistance to downy mildew by RT-PCR. Putative protein molecular weight was 113.7 kDa with an isoelectric point of 7.88 and no predicted transmembrane domain. It belonged to the TIR-NBS-LRR resistance gene based on putative amino acid sequence and contained all of conservative domains of TIR-NBS-LRR resistance genes. The deduced nucleic acid and amino acid sequence of MRGH-J shared 99% identity with the reported melon resistance gene analog MRGH12 and resistance to downy mildew gene mp-19,which suggested that it might be of great importance in melon disease resistance.