Agarrwal Ruchi, Padmakumari Ayyagari Phani, Bentur Jagadish S, Nair Suresh
International Centre for Genetic Engineering and Biotechnology (ICGEB), Aruna Asaf Ali Marg, New Delhi, 110067, India.
Indian Institute of Rice Research (formerly Directorate of Rice Research), Rajendranagar, Hyderabad, 500030, India.
Rice (N Y). 2016 Dec;9(1):5. doi: 10.1186/s12284-016-0077-6. Epub 2016 Feb 19.
An incompatible interaction between rice (Oryza sativa) and the Asian rice gall midge (AGM, Orseolia oryzae Wood-Mason), that is usually manifested through a hypersensitive response (HR), represents an intricate relationship between the resistant host and its avirulent pest. We investigated changes in the transcriptome and metabolome of the host (indica rice variety: RP2068-18-3-5, RP), showing HR when attacked by an avirulent gall midge biotype (GMB1), to deduce molecular and biochemical bases of such a complex interaction. Till now, such an integrated analysis of host transcriptome and metabolome has not been reported for any rice-insect interaction.
Transcript and metabolic profiling data revealed more than 7000 differentially expressed genes and 80 differentially accumulated metabolites, respectively, in the resistant host. Microarray data revealed deregulation of carbon (C) and nitrogen (N) metabolism causing a C/N shift; up-regulation of tetrapyrrole synthesis and down-regulation of chlorophyll synthesis and photosynthesis. Integrated results revealed that genes involved in lipid peroxidation (LPO) were up-regulated and a marker metabolite for LPO (azelaic acid) accumulated during HR. This coincided with a greater accumulation of GABA (neurotransmitter and an insect antifeedant) at the feeding site. Validation of microarray results by semi-quantitative RT-PCR revealed temporal variation in gene expression profiles.
The study revealed extensive reprogramming of the transcriptome and metabolome of RP upon GMB1 infestation leading to an HR that was induced by the generation and release of reactive oxygen species i.e. singlet oxygen and resulted in LPO-mediated cell death. RP thus used HR as a means to limit nutrient supply to the feeding maggots and simultaneously accumulated GABA, strategies that could have led to maggot mortality. The integrated results of transcript and metabolic profiling, for the first time, provided insights into an HR+ type of resistance in rice against gall midge.
水稻（Oryza sativa）与亚洲稻瘿蚊（AGM，Orseolia oryzae Wood-Mason）之间的不亲和互作通常通过过敏反应（HR）表现出来，这代表了抗性寄主与其无毒害虫之间的复杂关系。我们研究了寄主（籼稻品种：RP2068-18-3-5，RP）在受到无毒稻瘿蚊生物型（GMB1）攻击时表现出HR的转录组和代谢组变化，以推断这种复杂互作的分子和生化基础。到目前为止，尚未有关于任何水稻-昆虫互作的寄主转录组和代谢组的综合分析报道。
转录组和代谢谱分析数据分别显示，抗性寄主中有7000多个差异表达基因和80种差异积累代谢物。微阵列数据显示碳（C）和氮（N）代谢失调导致C/N比值变化；四吡咯合成上调，叶绿素合成和光合作用下调。综合结果表明，参与脂质过氧化（LPO）的基因上调，并且在HR期间LPO的标记代谢物（壬二酸）积累。这与取食部位γ-氨基丁酸（一种神经递质和昆虫拒食剂）的大量积累相吻合。通过半定量RT-PCR验证微阵列结果，揭示了基因表达谱的时间变化。
该研究揭示了RP在受到GMB1侵染后转录组和代谢组的广泛重编程，导致由活性氧即单线态氧的产生和释放诱导的HR，并导致LPO介导的细胞死亡。因此，RP利用HR作为限制取食蛆虫营养供应的手段，同时积累γ-氨基丁酸，这些策略可能导致蛆虫死亡。转录组和代谢谱的综合结果首次为水稻对稻瘿蚊的HR+型抗性提供了见解。
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