Diverse members of the AvrBs3/PthA family of type III effectors are major virulence determinants in bacterial blight disease of rice
Diverse members of the AvrBs3/PthA family of type III effectors are major virulence determinants in bacterial blight disease of rice
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DOI：
10.1094/mpmi.2004.17.11.1192
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发表时间：
2004-11-01
影响因子：
3.5
通讯作者：
White, FF
中科院分区：
文献类型：
--
作者：
Bing, Y;White, FF
AvrXa 7是avBs 3/pthA基因家族的一个成员，是唯一已知的水稻黄单胞菌致病变种的III型分泌系统效应基因。在水稻细菌性枯萎病中对细菌生长和病斑形成有主要贡献。我们通过鉴定来自病原体不同菌株的效应子，研究了水稻白叶枯病中AvrBs 3/PthA家族效应子的一般需求。在来自日本、韩国和菲律宾的代表性菌株中，单效应基因的失活导致植物的生长受到严重限制。其中5株病毒携带1个avrBs 3/pthA家族基因，1株病毒携带2个与avrXa 7毒力活性相当的基因。序列分析显示，与avrXa 7相比，3个基因具有独特的重复排列。重复区域的比较揭示了该组的一个潜在基序，该基序也存在于avrBs 3的重复区域中。然而，avrBs 3的重复区不能支持毒力活性，但与avrXa 7的C-末端编码区结合，触发了Xa 7依赖性无毒反应。结果表明，avrBs 3/pthA基因家族中有多种成员在X. oryzaepv.并支持了水稻白叶枯病高度依赖于一类III型效应子的假设。结果还表明avrXa 7的无毒特异性与毒力活性是可分离的。
AvrXa7 is a member of the avBs3/pthA gene family and the only known type III secretion system effector gene from Xanthomonas oryzae pv. oryzae with a major contribution to bacterial growth and lesion formation in bacterial blight disease of rice. We examined the general requirement for effectors of the AvrBs3/PthA family in bacterial blight of rice by identifying effectors from diverse strains of the pathogen. Inactivation of single effector genes in representative strains from Japan, Korea, and the Philippines resulted in severely limited growth in plants. Five strains harbored one gene of the avrBs3/pthA family, while one strain had two genes with the equivalent virulence activity of avrXa7. Sequence analysis revealed three genes with unique repeat arrangements in comparison to avrXa7. Comparison of the repetitive regions revealed a potential motif for the group that was also present in the repetitive region of avrBs3. However, the repetitive region of avrBs3 could not support virulence activity but, in combination with the C-terminal coding region of avrXa7, triggered a Xa7-dependent avirulence reaction. The results revealed diverse members of the avrBs3/pthA gene family with virulence activity in X. oryzae pv. oryzae and supported the hypothesis that bacterial blight disease of rice is highly dependent on a single class of type III effectors. The results also indicated that avrXa7 avirulence specificity is separable from virulence activity.