Aims

Climate change is affecting rainfall patterns causing intermittent drought stress to rainfed rice. It is poorly understood how intermittent drought impacts the blast of rice incited by Magnaporthe oryzae.

Methods

The impact of intermittent drought on virulence factors of Magnaporthe oryzae and defense responses in blast resistant (C101A51 and Tetep), susceptible (HR-12) and drought-tolerant (Vandana) rice cultivars was analyzed in stress overlapped conditions. Transcript accumulation of rice defense genes, histone acetyltransferases (OsHATs) and pathogenesis-associated genes of M. oryzae was recorded and histone acetylation at H3K9 and H4K5 was assessed through western blotting.

Results

Predisposition to intermittent drought favored blast development in all rice cultivars. Higher blast resistance in C101A51 is linked to enhanced histone acetylation at H3K9 compared to Tetep. However, intermittent drought predisposition caused partial breakdown of blast resistance due to reduced OsHAT activities that led to reduced histone acetylation at H3K9. ABA signaling was predominant in drought predisposed and M. oryzae challenged plants compared to SA signaling in only M. oryzae challenged plants. Interestingly, pathogenesis-associated genes (chitin synthases, chitin deacetylases, appressorium formation) of M. oryzae were highly expressed in the drought predisposed plants compared to only M. oryzae challenged plants.

Conclusions

Intermittent drought induces vulnerability of rice to blast disease. Vulnerability of rice to the pathogen in drought predisposed conditions is attributed to reduced activities of the histone acetyltransferases (OsHATs), masking of SA-signaling by ABA-signaling as well as enhanced activities of pathogenesis-associated genes in M. oryzae.

中文翻译：

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间歇性干旱会对水稻对稻瘟病菌稻瘟病菌的单基因抗性产生不利影响，并与组蛋白乙酰化的改变有关

 目标

气候变化正在影响降雨模式，对雨养水稻造成间歇性干旱胁迫。人们对间歇性干旱如何影响稻瘟病引起的稻瘟病知之甚少。

 方法

在胁迫重叠条件下，分析了间歇性干旱对稻瘟病菌毒力因子以及抗稻瘟病（C101A51 和 Tetep）、感病（HR-12）和耐旱（Vandana）水稻品种防御反应的影响。记录水稻防御基因、组蛋白乙酰转移酶 ( OsHAT ) 和米霉发病机制相关基因的转录积累，并通过蛋白质印迹评估 H3K9 和 H4K5 的组蛋白乙酰化。

 结果

间歇性干旱的倾向有利于所有水稻品种的稻瘟病的发生。与 Tetep 相比，C101A51 中较高的稻瘟病抗性与 H3K9 处的组蛋白乙酰化增强有关。然而，间歇性干旱易感性导致稻瘟病抗性部分崩溃，因为OsHAT活性降低，导致 H3K9 组蛋白乙酰化减少。与仅在受米霉攻击的植物中SA信号传导相比，ABA信号传导在易受干旱影响且受米霉攻击的植物中占主导地位。有趣的是，与仅受米霉攻击的植物相比，米霉的发病机制相关基因（几丁质合酶、几丁质脱乙酰酶、附着胞形成）在易受干旱影响的植物中高度表达。

 结论

间歇性干旱导致水稻易受稻瘟病影响。水稻在干旱易感条件下对病原体的脆弱性归因于组蛋白乙酰转移酶 ( OsHAT ) 活性降低、ABA 信号屏蔽 SA 信号以及米霉中发病机制相关基因的活性增强。