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野油菜黄单胞菌(Xanthomonas campestris pv.campestris,Xcc)通过III型分泌系统分泌效应蛋白到植物体内,帮助其在植物体内侵染和繁殖。XopXccN是野油菜黄单胞菌Xcc8004菌株的一个效应蛋白,利用同源重组双交换法将基因xop Xcc N在Xcc8004的基因组上做了删除突变,并对突变菌株进行了遗传互补。通过在拟南芥叶片上接种野生型Xcc8004、突变体菌株Δxop Xcc N以及互补菌株Δxop Xcc NC,发现效应蛋白XopXccN对于Xcc8004在拟南芥叶肉组织内的完整毒性是必须的。进一步研究发现,XopXccN可以抑制鞭毛蛋白诱导的MAPK激酶活性,其抑制发生在MKK下游。另外,XopXccN还可以抑制鞭毛蛋白诱导的下游标志基因FRK1(g22-induced receptor-like kinase)的表达。将XopXccN蛋白分段表达后发现,对于FRK1基因表达的抑制依赖于XopXccN的全长蛋白序列。本研究结果表明,XopXccN通过抑制M APK激酶活性,从而抑制寄主的先天免疫反应。
Xanthomonas campestris pv. Campestris (Xcc) secretes effector proteins into plants through the type III secretion system, helping it to infect and multiply in plants. XopXccN is a effector protein of Xcc8004 strain of Xanthomonas campestris. The gene xop Xcc N was deleted and mutated in the genome of Xcc8004 by homologous recombination double crossover, and the mutants were genetically complemented. The effector protein XopXccN was found to be essential for the complete toxicity of Xcc8004 in Arabidopsis thaliana mesophyll by inoculation of wild-type Xcc8004, mutant strain Δxop Xcc N and the complementary strain Δxop Xcc NC on Arabidopsis leaves. Further study found that XopXccN can inhibit flagellin-induced MAPK kinase activity, the inhibition occurred in the MKK downstream. In addition, XopXccN can also inhibit flagellin-induced expression of the downstream marker gene FRK1 (g22-induced receptor-like kinase). Fragmenting the XopXccN protein revealed that the inhibition of FRK1 gene expression was dependent on the full-length protein sequence of XopXccN. The results of this study indicate that XopXccN inhibits the host innate immune response by inhibiting M-APK kinase activity.