Cloning of immunodominant membrane protein genes of phytoplasmas and their in planta expression
Cloning of immunodominant membrane protein genes of phytoplasmas and their in planta expression
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DOI：
10.1111/j.1574-6968.2009.01509.x
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发表时间：
2009-04-01
影响因子：
2.1
通讯作者：
Namba, Shigetou
中科院分区：
文献类型：
--
作者：
Kakizawa, Shigeyuki;Oshima, Kenro;Namba, Shigetou
植原体是植物病原细菌，会导致全世界多种作物遭受毁灭性的产量损失。尽管了解病原体生物学在农业中很重要，但无法培养植原体阻碍了对其的全面表征。以往的研究表明，免疫显性膜蛋白可分为免疫显性膜蛋白（Imp）、免疫显性膜蛋白A（IdpA）和抗原性膜蛋白（Amp）三种类型，并且它们之间是非同源的。在这里，对包括紫菀黄和稻黄矮群在内的几类植原体进行了含有imp的基因组片段的克隆和测序，此前尚未报道过这些植原体的imp序列。序列比较分析表明，Imp在植原体之间差异很大，并且在几个Imp中观察到明显的正选择，这表明Imp在宿主-植原体相互作用中发挥重要作用。由于已知洋葱黄 (OY) 植原体含有 Amp 作为免疫显性膜蛋白，因此测量了植物中 Imp 的蛋白质积累水平，并与 Amp 的蛋白质积累水平进行比较。由此产生的 Imp 累积量经计算约为 Amp 的十分之一，与 OY 中 Amp 的免疫显性特性一致。这表明免疫显性膜蛋白的祖先类型可能是Imp，随后在几个植原体类群中Amp或IdpA的表达水平增加。
Phytoplasmas are plant pathogenic bacteria that cause devastating yield losses in diverse crops worldwide. Although the understanding of the pathogen biology is important in agriculture, the inability to culture phytoplasmas has hindered their full characterization. Previous studies demonstrated that immunodominant membrane proteins could be classified into three types, immunodominant membrane protein (Imp), immunodominant membrane protein A (IdpA), and antigenic membrane protein (Amp), and they are nonhomologous to each other. Here, cloning and sequencing of imp-containing genomic fragments were performed for several groups of phytoplasma including the aster yellows and rice yellow dwarf groups, for which an imp sequence has not previously been reported. Sequence comparison analysis revealed that Imps are highly variable among phytoplasmas, and clear positive selection was observed in several Imps, suggesting that Imp has important roles in host-phytoplasma interactions. As onion yellows (OY) phytoplasma was known to have Amp as the immunodominant membrane protein, the protein accumulation level of Imp in planta was measured compared with that of Amp. The resulting accumulation of Imp was calculated as approximately one-tenth that of Amp, being consistent with the immunodominant property of Amp in OY. It is suggested that an ancestral type of immunodominant membrane protein could be Imp, and subsequently the expression level of Amp or IdpA is increased in several phytoplasma groups.