Abstract：
Sheath blight disease of rice caused by a soil-borne fungal pathogen Rhizoctonia solani AG1-IA is one of the major threats to rice production globally. During host-pathogen interactions, reactive oxygen species (ROS) play an important role in pathogen virulence and plant defense. For example, necrotrophic pathogens induce ROS production to damage host cells, whereas the host can incite ROS to kill the pathogen. From the host perspective, it is essential to understand how the antioxidant machinery maintains a delicate balance of ROS to protect itself from its lethal effects. Here, we investigated the pathogen-induced accumulation of ROS and implicated damage in two rice genotypes (PR114, susceptible; ShB, moderately tolerant) varying in the level of susceptibility to R. solani AG1-IA. Compared to PR114, ShB exhibited a better antioxidant response and reasonably lesser oxidative damage. Further, we observed elevated levels of jasmonic acid (JA) in ShB, which was otherwise decreased in PR114 in response to pathogen infection. As depicted, an elevated level of JA was in agreement with the expression profiles of genes involved in its biosynthesis and signaling. To further ascertain if the heightened antioxidant response is JA-dependent or independent, methyl jasmonate (MeJA) was exogenously applied to PR114, and antioxidant response in terms of gene expression, enzyme activities, and oxidative damage was studied in R. solani infected samples. Surprisingly, the exogenous application of MeJA complemented the antioxidant response and reduced oxidative damage in PR114, thus suggesting that the antioxidant defense system is under transcriptional control of JA.
摘要：
由土壤传播的真菌病原体枯萎病引起的水稻纹枯病是全球水稻生产的主要威胁之一。在宿主-病原体相互作用期间，活性氧（ROS）在病原体毒力和植物防御中起重要作用。例如,坏死病原体诱导ROS产生以损伤宿主细胞，而宿主可以激发ROS杀死病原体。从主持人的角度来看,了解抗氧化机制如何保持ROS的微妙平衡以保护自身免受致命影响是至关重要的。这里,我们调查了两种水稻基因型(PR114，易感；ShB，中等耐受性)对索兰尼AG1-IA的易感性水平不同。与PR114相比，ShB表现出更好的抗氧化反应和相当小的氧化损伤。Further,我们观察到ShB中茉莉酸（JA）水平升高，否则在PR114中由于病原体感染而降低。如图所示，JA水平的升高与参与其生物合成和信号传导的基因的表达谱一致。为了进一步确定增强的抗氧化反应是依赖JA还是独立的，茉莉酸甲酯（MeJA）被外源应用于PR114，在基因表达方面的抗氧化反应，酶活性，和氧化损伤在R.solani感染的样品中进行了研究。令人惊讶的是,MeJA的外源应用补充了PR114中的抗氧化反应并减少了氧化损伤，因此表明抗氧化防御系统处于JA的转录控制之下。
