The State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100081, China.
Appl Microbiol Biotechnol. 2019 Aug;103(15):6153-6167. doi: 10.1007/s00253-019-09937-2. Epub 2019 Jun 1.
MoHrip2, identified from Magnaporthe oryzae as an elicitor, can activate plant defense responses either in the form of recombinant protein in vitro or ectopic expressed protein in rice. However, its intrinsic function in the infective interaction of M. oryzae-rice is largely unknown. Here, we found that mohrip2 expression was significantly induced at stages of fungal penetration and colonization. Meanwhile, the induced MoHrip2 mainly accumulated in the rice apoplast by outlining the entire invasive hyphae during infection, and its secretion was via the conventional endoplasmic reticulum (ER)-to-Golgi pathway, demonstrating the nature of MoHrip2 as an apoplastic effector. What's more, the disease facilitating function of MoHrip2 was revealed by the significantly compromised virulence of Δmohrip2 mutants on rice seedlings and even on the wounded rice leaves. Inoculations of these mutant strains on rice leaf sheaths showed a reduction in penetration and subsequent expansion of fungal growth, which is probably due to activated host immunity including the expression of certain defense-related genes and the production of certain phytoalexins. Altogether, these results demonstrated the necessity of MoHrip2 in suppression of host immunity and the full virulence of M. oryzae.
MoHrip2 是从稻瘟病菌中鉴定出的一种激发子，无论是以重组蛋白的形式在体外还是在水稻中外源表达蛋白，都能激活植物的防御反应。然而，其在稻瘟病菌与水稻互作中的固有功能在很大程度上尚不清楚。在这里，我们发现 mohrip2 的表达在真菌穿透和定殖阶段显著上调。同时，诱导的 MoHrip2 主要通过在侵染过程中勾勒出整个侵入性菌丝而在水稻质外体中积累，其分泌是通过传统的内质网 (ER)-高尔基体途径进行的，这表明 MoHrip2 是一种质外体效应子。更重要的是，通过 Δmohrip2 突变体在水稻幼苗甚至受伤的水稻叶片上的毒力显著降低，揭示了 MoHrip2 的促病功能。将这些突变菌株接种到水稻叶鞘上，显示出穿透减少和随后的真菌生长扩张，这可能是由于宿主免疫的激活，包括某些防御相关基因的表达和某些植保素的产生。总之，这些结果表明 MoHrip2 在抑制宿主免疫和稻瘟病菌的完全毒力方面是必要的。
