Feng T, Zhang ZY, Gao P, Feng ZM, Zuo SM, Ouyang SQ.

Int J Mol Sci. 2023 Feb 11;24(4):3653. doi: 10.3390/ijms24043653.

Abstract

MicroRNAs (miRNAs) are a class of conserved small RNA with a length of 21-24 nucleotides in eukaryotes, which are involved in development and defense responses against biotic and abiotic stresses. By RNA-seq, Osa-miR444b.2 was identified to be induced after Rhizoctonia solani (R. solani) infection. In order to clarify the function of Osa-miR444b.2 responding to R. solani infection in rice, transgenic lines over-expressing and knocking out Osa-miR444b.2 were generated in the background of susceptible cultivar Xu3 and resistant cultivar YSBR1, respectively. Over-expressing Osa-miR444b.2 resulted in compromised resistance to R. solani. In contrast, the knocking out Osa-miR444b.2 lines exhibited improved resistance to R. solani. Furthermore, knocking out Osa-miR444b.2 resulted in increased height, tillers, smaller panicle, and decreased 1000-grain weight and primary branches. However, the transgenic lines over-expressing Osa-miR444b.2 showed decreased primary branches and tillers, but increased panicle length. These results indicated that Osa-miR444b.2 was also involved in regulating the agronomic traits in rice. The RNA-seq assay revealed that Osa-miR444b.2 mainly regulated the resistance to rice sheath blight disease by affecting the expression of plant hormone signaling pathways-related genes such as ET and IAA, and transcription factors such as WRKYs and F-boxes. Together, our results suggest that Osa-miR444b.2 negatively mediated the resistance to R. solani in rice, which will contribute to the cultivation of sheath blight resistant varieties.

See https://pubmed.ncbi.nlm.nih.gov/36835070/

Figure 1

Rice sheath blight disease symptoms and Osa-miR444b.2 was induced by R. solani infection. (A) R. solani inoculation and disease severity of susceptible cultivar Xu3 and resistant cultivar YSBR1. (B) Statistics of lesion length in Xu3 and YSBR1 at different time points. Data are Mean ± SD (four independent plants). (C) The transcript level of Osa-miR444b.2 wasinduced by the infection of R. solani. Total RNA samples (10 μg) were used for northern blot analysis. The loading control was presented using a U6 probe. Blots were imaged using a phosphorimager, and measured to the grey density using Image J software. The numbers below each blot presented the relative enrichment of Osa-miR444b.2 in each treatment normalized to the corresponding water-treated control. XC: Xu3 treated by water as control, XT: Xu3 infected by R. Solani, YC: YSBR1 treated by water as control, YT: YSBR1 infected by R. Solani.