Park Young Ju, Lee Hwa Jung, Kwak Kyung Jin, Lee Kwanuk, Hong Suk Whan, Kang Hunseung
Department of Plant Biotechnology, College of Agriculture and Life Sciences, Chonnam National University, 300 Yongbong-dong, Buk-gu, Gwangju 500-757, Republic of Korea These authors contributed equally to this work.
Department of Plant Biotechnology, College of Agriculture and Life Sciences, Chonnam National University, 300 Yongbong-dong, Buk-gu, Gwangju 500-757, Republic of Korea.
Plant Cell Physiol. 2014 Sep;55(9):1660-8. doi: 10.1093/pcp/pcu096. Epub 2014 Jul 8.
Although a large number of microRNAs (miRNAs) have been identified in different plant species, the functional roles and targets of the majority of miRNAs have not yet been determined. Here, Arabidopsis thaliana miRNA400 (miR400) was investigated for its functional role in the defense response to diverse pathogens. Transgenic Arabidopsis plants that overexpress MIR400 (35S::MIR400) displayed much more severe disease symptoms than the wild-type plants when infected with the bacterium Pseudomonas syringae pv. tomato DC3000 or the fungus Botrytis cinerea. MiR400 guided the cleavage of two genes (At1g06580 and At1g62720) encoding pentatricopeptide repeat (PPR) proteins. To confirm further that the miR400-mediated defense response was due to the cleavage of PPR mRNAs, loss-of-function mutant and artificial miRNA-mediated knockdown mutants of PPR were generated, and their disease responses were analyzed upon pathogen challenge. Similar to the 35S::MIR400 plants, the ppr mutants displayed much more severe disease symptoms than the wild-type plants when challenged with the pathogens, indicating that miR400 affects the defense response by cleaving PPR mRNAs. Expression of miR400 was down-regulated, whereas the PPR1 and PPR2 transcripts increased upon pathogen challenge. Collectively, the present study reveals that miR400-mediated dysfunction of PPR proteins renders Arabidopsis more susceptible to pathogenic bacteria and fungi, which emphasizes the importance of PPR proteins in plant defense against diverse pathogens.
尽管在不同植物物种中已鉴定出大量微小RNA（miRNA），但大多数miRNA的功能作用和靶标尚未确定。在此，对拟南芥miRNA400（miR400）在对多种病原体的防御反应中的功能作用进行了研究。当用丁香假单胞菌番茄致病变种DC3000或灰葡萄孢菌感染时，过表达MIR400的转基因拟南芥植株（35S::MIR400）比野生型植株表现出更严重的病害症状。miR400引导了两个编码五肽重复（PPR）蛋白的基因（At1g06580和At1g62720）的切割。为了进一步证实miR400介导的防御反应是由于PPR mRNA的切割，构建了PPR的功能缺失突变体和人工miRNA介导的敲低突变体，并分析了它们在病原体攻击后的病害反应。与35S::MIR400植株相似，ppr突变体在受到病原体攻击时比野生型植株表现出更严重的病害症状，表明miR400通过切割PPR mRNA影响防御反应。在病原体攻击后，miR400的表达下调，而PPR1和PPR2转录本增加。总的来说，本研究揭示了miR400介导的PPR蛋白功能障碍使拟南芥对致病细菌和真菌更易感，这强调了PPR蛋白在植物抵御多种病原体中的重要性。
