Yucel I, Boyd C, Debnam Q, Keen N T
Department of Plant Pathology, University of California, Riverside 92521.
Mol Plant Microbe Interact. 1994 Jan-Feb;7(1):131-9. doi: 10.1094/mpmi-7-0131.
Considerable variation was observed in the occurrence of avirulence gene D (avrD) in different isolates and pathovars of Pseudomonas syringae. Three functional alleles of avrD were cloned and characterized from P. s. pv. phaseolicola and P. s. pv. lachrymans. These avrD genes occurred on indigenous plasmids in both pathovars, like the allele originally cloned from P. s. pv. tomato. P. s. pv. lachrymans was unique in that it carried two different alleles on plasmids of different sizes. These alleles were cloned on 5.6- or 3.8-kb HindIII fragments that are conserved in several other P. syringae pathovars. Surprisingly, the two avrD alleles from P. s. pv. lachrymans were the most divergent of those compared, with only 85% amino acid identity. Allele 1 from P. s. pv. lachrymans was 95% identical to avrD from P. s. pv. tomato but less similar to the other three avrD genes. These two alleles were accordingly called homology class I. The avrD gene from P. s. pv. phaseolicola and allele 2 from P. s. pv. lachrymans were 97 and 98% identical, respectively, at the amino acid level with the nonfunctional P. s. pv. glycinea allele. These three alleles were therefore grouped into homology class II. Comparison of all the avrD alleles permitted the identification of four amino acid substitutions unique to the P. s. pv. glycinea allele at positions 19, 245, 280, and 304.
在丁香假单胞菌不同分离株和致病变种中，无毒基因D（avrD）的出现情况存在显著差异。从菜豆丁香假单胞菌和黄瓜角斑病丁香假单胞菌中克隆并鉴定了avrD的三个功能等位基因。这些avrD基因存在于这两个致病变种的内源质粒上，就像最初从番茄丁香假单胞菌中克隆的等位基因一样。黄瓜角斑病丁香假单胞菌的独特之处在于，它在不同大小的质粒上携带了两个不同的等位基因。这些等位基因克隆在5.6或3.8 kb的HindIII片段上，这些片段在其他几种丁香假单胞菌致病变种中是保守的。令人惊讶的是，来自黄瓜角斑病丁香假单胞菌的两个avrD等位基因在比较的等位基因中差异最大，氨基酸同一性仅为85%。来自黄瓜角斑病丁香假单胞菌的等位基因1与来自番茄丁香假单胞菌的avrD有95%的同一性，但与其他三个avrD基因的相似性较低。因此，这两个等位基因被称为同源I类。菜豆丁香假单胞菌的avrD基因和黄瓜角斑病丁香假单胞菌的等位基因2在氨基酸水平上分别与无功能的大豆疫霉等位基因有97%和98%的同一性。因此，这三个等位基因被归为同源II类。对所有avrD等位基因的比较使得能够鉴定出大豆疫霉等位基因在第19、245、280和304位上特有的四个氨基酸取代。
