ZmTrxh介导的抵御甘蔗花叶病毒及与玉米褪绿斑驳病毒协同侵染玉米的抗病调控机制解析

Sugarcane mosaic virus (SCMV) is the main pathogen of maize dwarf mosaic disease in China. ZmTrxh was validated via transgenic complementation test to be the causal gene at the Scmv1 locus, however, the underlying mechanism remains largely unknown. Maize lethal necrosis disease currently occurs only in Yunnan province of China, which is caused by co-infection with maize chlorotic mottle virus (MCMV) and SCMV. Our previous study confirmed that ZmTrxh exhibited resistance to MCMV and its synergistic interaction with SCMV in maize. Based on these results, this project aims to understand the immune-regulatory network mediated by ZmTrxh to against SCMV or/and its synergistic interaction with MCMV in maize, by combining functional genomics techniques, such as molecular biology, ribosome profiling, ultrastructural investigations. In this study we look forward to identify the possible genes involved in the pathway of maize resistance responses to viral attack on a genome-wide scale. Our findings will not only help to reveal the molecular mechanisms of maize resistance to SCMV and MCMV mediated by ZmTrxh, but also provide theoretical support for developing resistant variety and preventing maize lethal necrosis disease epidemics in China. The results of this project make it of great value in theory and practical application.

玉米矮花叶病在我国由甘蔗花叶病毒（Sugarcan mosaic virus, SCMV）侵染导致，主效抗病基因ZmTrxh已克隆但其介导的抗病机制尚待解析。玉米致死性坏死病仅在我国云南等少数地区发现且均由玉米褪绿斑驳病毒（Maize chlorotic mottle virus, MCMV）协同SCMV复合侵染所致。前期研究发现ZmTrxh对MCMV协同SCMV侵染玉米表现抗性。本项目拟通过分子生物学、翻译组学结合细胞超微结构检测，剖析ZmTrxh在不同免疫响应层面介导的抵御SCMV单独及协同MCMV侵染的抗病调控网络，高通量筛选鉴定参与“单一/复合病毒—玉米寄主”互作网络的关键功能基因。本项目预期结果有助于揭示ZmTrxh介导的抵御SCMV单独/协同MCMV侵染抗病分子机制；也为培育玉米抗病品种、有效防止玉米矮花叶病及玉米致死性坏死病在我国蔓延提供科学依据，兼具理论意义和应用价值。

本项目在玉米矮花叶病主效抗病基因ZmTrxh已完成克隆的基础上，通过分子生物学、组学结合生理生化检测，剖析ZmTrxh介导的抵御甘蔗花叶病毒（Sugarcan mosaic virus，SCMV）单独及与玉米褪绿斑驳病毒（Maize chlorotic mottle virus，MCMV）协同侵染的免疫调控网络，筛选鉴定参与抗病毒防御反应的关键功能基因。主要研究结果如下：利用近等基因系材料及玉米原生质体瞬时表达系统证实ZmTrxh能够有效抵御SCMV单独及协同MCMV早期对玉米寄主的侵染，限制SCMV及MCMV基因组RNA的复制与长距离移动，延迟和削弱玉米致死性坏死病的发病时间和程度。甘蔗花叶病毒中的HC-Pro蛋白、VPg蛋白以及玉米褪绿斑驳病毒中的P31蛋白可能是病毒入侵玉米寄主早期阶段最先利用寄主翻译系统的关键致病蛋白；相比于甘蔗花叶病毒单一病毒侵染，协同侵染过程中甘蔗花叶病毒的HC-Pro蛋白数量明显在翻译水平提高，暗示甘蔗花叶病毒编码的HC-Pro蛋白可能涉及复合侵染玉米寄主并加重感病程度的致病机制。联合转录组及翻译组数据，挖掘到277个差异表达的基因可能参与对协同侵染的抗性调控机制，通过GO分析和KEGG pathway分析，这些差异基因在胁迫与防御反应、光合作用、植物激素合成、信号转导、三羧酸循环、代谢途径等通路显著富集，而且上调和下调的基因无论在数量上还是调节程度上均要比单一侵染明显。玉米寄主叶绿体、线粒体在复合侵染中也比单一病毒侵染更早遭到破坏且严重。本项目初步探索了ZmTrxh介导的抵御SCMV单独/协同MCMV侵染的抗病分子机制，也为培育玉米抗病品种、有效防止玉米矮花叶病及玉米致死性坏死病在我国蔓延提供科学依据，兼具理论意义和应用价值。