稻瘟病菌无毒蛋白AvrPiz-t半胱氨酸残基的功能分析

Functional analysis of cysteine residues of the Magnaporthe oryzae avirulence protein AvrPiz-t

稻瘟病菌无毒基因AvrPiz-t编码了一个包含108个氨基酸的未知功能的预测分泌蛋白,其与对应的水稻抗稻瘟病基因Piz-t介导了基因对基因的抗病反应。序列分析发现AvrPiz-t的预测成熟蛋白AvrPiz-t90含有4个半胱氨酸残基,推测它们可能参与了AvrPiz-t蛋白分子内或分子间的相互作用。为了检测这4个半胱氨酸对AvrPiz-t功能的影响,利用定点突变技术对4个半胱氨酸残基分别进行了位点突变并构建了相应的稻瘟病菌互补载体。功能互补分析发现,上述4个突变体都丧失了AvrPiz-t无毒基因的功能。由此推断,半胱氨酸对AvrPiz-t蛋白功能的表达是非常重要的。

The Magnaporthe oryzae avirulence gene AvrPiz-t encodes a small predicted secreted protein （ 108 amino acids） without known function and mediates resistance in a gene-for-gene fashion to Piz-t in rice. Sequence analysis of AvrPiz-t revealed that its predicted mature form AvrPiz-tgo consists of 4 cysteine residues, which is predicted to be involved in intra- and intermolecular interactions. To further investigate the signifi- cance of these 4 cysteine residues in the function of AvrPiz-t, a site-mutagenesis approach was utilized to ge- nerate 4 constructs encompassing mutations at each cysteine residue. Complementation tests revealed that these 4 derived AvrPiz-t mutants lost avirulence function to Piz-t, which indicated that these 4 cysteine residues were critical for the avirulence function of AvrPiz-t.