Ling-Li Zhang , Yan Li , Ya-Ping Zheng, He Wang, Xuemei Yang, Jin-Feng Chen, Shi-Xin Zhou, Liang-Fang Wang, Xu-Pu Li , Xiao-Chun Ma , Ji-Qun Zhao, Mei Pu, Hui Feng, Jing Fan, Ji-Wei Zhang, Yan-Yan Huang, Wen-Ming Wang

Front Genet 2020 Apr 23;11:327.  doi: 10.3389/fgene.2020.00327. eCollection 2020.

Abstract

MicroRNAs (miRNAs) play essential roles in the regulation of plant growth and defense responses. More and more, miRNA-3ps are reported to act in plant development and immunity. miR156 is a conserved miRNA, and most previous studies focus on its roles in plant growth, development, and yield determinacy. Here, we show that expressing a target mimic of miR156fhl-3p led to enhanced rice blast disease resistance without a yield penalty. miR156fhl-3p was differentially responsive to Magnaporthe oryzae in susceptible and resistant accessions. Transgenic lines expressing a target mimic of miR156fhl-3p (MIM156-3p) exhibited enhanced rice blast disease resistance and increased expression of defense-related genes. MIM156-3p also enhanced the mRNA abundance of SPL14 and WRKY45 by down-regulating miR156-5p and pre-miR156. Moreover, MIM156-3p lines displayed a decreased number of second rachis branches per panicle but enlarged grains, leading to unchanged yield per plant. Consistently, overexpressing miR156h (OX156) led to enhanced susceptibility to M. oryzae and decreased the expression of SPL14 and WRKY45. Our results indicate that miR156fhl-3p mounts a regulatory role on miR156-5p, which subsequently regulates the expression of SPL14 and WRKY45 to improve rice blast disease resistance.

See https://www.frontiersin.org/articles/10.3389/fgene.2020.00327/full

Figure 6. Blocking miR156fhl-3p releases SPL14 from suppression by miR156-5p. (A) Confocal images show the protein levels of SPL14_TBS-YFP, SPL14_MBS-YFP, and YFP co-expressed with miR156 or with miR156 and MIM156-3p. The indicated SPL14_TBS-YFP, SPL14_MBS-YFP, and YFP reporter constructs were transiently expressed alone or co-expressed with miR156 and MIM156-3p in N. benthamiana leaves by Agrobacterium-mediated transformation at the indicated optical density (O.D.) concentration. Size bars, 50 μm. (B) Western blotting analysis shows the protein abundance of SPL14_TBS-YFP, SPL14_MBS-YFP, and YFP. Protein extracts from infiltrated leaves were collected for Western blot analysis using anti-GFP sera and anti-Rubisco sera, respectively. These experiments were repeated two times with similar results.