Keith L W, Boyd C, Keen N T, Partridge J E
Department of Plant Pathology, University of Nebraska, Lincoln 68583-0722, USA.
Mol Plant Microbe Interact. 1997 Apr;10(3):416-22. doi: 10.1094/MPMI.1997.10.3.416.
Avirulence gene D alleles resided on indigenous plasmids in races 0, 2, 3, 4, 5, and 6 of Pseudomonas syringae pv. glycinea (Psg), but the allele in race 1 appeared to be chromosomal. These were all nonfunctional avirulence genes because they neither induced the avirulence phenotype on Rpg4 soybean cultivars nor directed the production of syringolide elicitors when expressed in Escherichia coli cells. The predicted proteins encoded by the seven Psg avrD genes were very similar to that of a functional class II allele from P. syringae pv. phaseolicola G50 race 2, but contained mutations collectively affecting only nine amino acid positions. Despite these relatively small amino acid differences and the location of avrD from each isolate on a 5.6-kb HindIII restriction fragment, the flanking regions varied considerably among the Psg isolates. The presence of avrD alleles with few alterations but different locational contexts in all tested Psg races argues that they provide an important selected function in the bacteria but have been modified to escape defense surveillance in Rpg4 soybean plants.
无毒基因D等位基因存在于大豆丁香假单胞菌（Psg）0、2、3、4、5和6号生理小种的内源质粒上，但1号生理小种中的等位基因似乎位于染色体上。这些都是无功能的无毒基因，因为它们既不会在携带Rpg4基因的大豆品种上诱导无毒表型，在大肠杆菌细胞中表达时也不会指导丁香酚内酯激发子的产生。七个Psg avrD基因编码的预测蛋白与来自菜豆丁香假单胞菌G50 2号生理小种的功能性II类等位基因的预测蛋白非常相似，但总共仅包含影响九个氨基酸位置的突变。尽管这些氨基酸差异相对较小，且每个分离株的avrD位于5.6 kb HindIII限制性片段上，但Psg分离株之间的侧翼区域差异很大。在所有测试的Psg生理小种中都存在改变很少但位置背景不同的avrD等位基因，这表明它们在细菌中提供了重要的选择功能，但已被修饰以逃避Rpg4大豆植物中的防御监测。
