Centre for Research in Agricultural Genomics (CRAG) CSIC-IRTA-UAB-UB. Edifici CRAG, Campus UAB, Bellaterra (Cerdanyola del Vallés), 08193 Barcelona, Spain.
Department of Molecular Biology, Max Planck Institute for Developmental Biology, 72076 Tübingen, Germany.
Sci Rep. 2017 Mar 23;7:44898. doi: 10.1038/srep44898.
MicroRNAs (miRNAs) play a pivotal role in regulating gene expression during plant development. Although a substantial fraction of plant miRNAs has proven responsive to pathogen infection, their role in disease resistance remains largely unknown, especially during fungal infections. In this study, we screened Arabidopsis thaliana lines in which miRNA activity has been reduced using artificial miRNA target mimics (MIM lines) for their response to fungal pathogens. Reduced activity of miR396 (MIM396 plants) was found to confer broad resistance to necrotrophic and hemibiotrophic fungal pathogens. MiR396 levels gradually decreased during fungal infection, thus, enabling its GRF (GROWTH-REGULATING FACTOR) transcription factor target genes to trigger host reprogramming. Pathogen resistance in MIM396 plants is based on a superactivation of defense responses consistent with a priming event during pathogen infection. Notably, low levels of miR396 are not translated in developmental defects in absence of pathogen challenge. Our findings support a role of miR396 in regulating plant immunity, and broaden our knowledge about the molecular players and processes that sustain defense priming. That miR396 modulates innate immunity without growth costs also suggests fine-tuning of miR396 levels as an effective biotechnological means for protection against pathogen infection.
MicroRNAs (miRNAs) 在植物发育过程中调节基因表达中起着关键作用。尽管大量植物 miRNAs 已被证明对病原体感染有反应，但它们在抗病性中的作用在很大程度上仍然未知，尤其是在真菌感染时。在这项研究中，我们使用人工 miRNA 靶标模拟物（MIM 系）筛选了 miRNA 活性降低的拟南芥系，以研究它们对真菌病原体的反应。miR396 的活性降低（MIM396 植物）被发现赋予了对坏死和半活体真菌病原体的广泛抗性。miR396 水平在真菌感染过程中逐渐降低，从而使其 GRF（生长调节因子）转录因子靶基因能够触发宿主重编程。MIM396 植物中的病原体抗性基于防御反应的超级激活，与病原体感染期间的启动事件一致。值得注意的是，在没有病原体挑战的情况下，miR396 的低水平不会导致发育缺陷。我们的研究结果支持 miR396 在调节植物免疫中的作用，并拓宽了我们对维持防御启动的分子参与者和过程的认识。miR396 调节先天免疫而不影响生长成本，这也表明精细调节 miR396 水平是一种有效的生物技术手段，可用于防止病原体感染。
