OsmiR5519 regulates grain size and weight and down-regulates sucrose synthase gene RSUS2 in rice (Oryza sativa L.).

Shengyuan Guo, Yajuan Li, Yan Wang, Yangwen Xu, Yuting Li, Ping Wu, Jinwen Wu, Lan Wang, Xiangdong Liu, Zhixiong Chen

Planta 2024 Mar 30

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The up-regulation of OsmiR5519 results in the decrease of grain size, weight and seed setting rate. OsmiR5519 plays important roles in the process of grain filling and down-regulates sucrose synthase gene RSUS2. MicroRNAs (miRNAs) are one class of small non-coding RNAs that act as crucial regulators of plant growth and development. In rice, the conserved miRNAs were revealed to regulate the yield components, but the function of rice-specific miRNAs has been rarely studied. The rice-specific OsmiR5519 was found to be abundantly expressed during reproductive development, but its biological roles remain unknown. In this study, the function of rice-specific OsmiR5519 was characterized with the miR5519-overexpressing line (miR5519-OE) and miR5519-silenced line (STTM5519). At seedling stage, the content of sucrose, glucose and fructose was obviously lower in the leaves of miR5519-OE lines than those of wild-type (WT) line. The grain size and weight were decreased significantly in miR5519-OE lines, compared to those of WT rice. The cell width of hull in miR5519-OE was smaller than that in WT. The seed setting rate was notably reduced in miR5519-OE lines, but not in STTM5519 lines. Cytological observation demonstrated that the inadequate grain filling was the main reason for the decline of seed setting rate in miR5519-OE lines. The percentage of the defects of grain amounted to 40% in miR5519-OE lines, which almost equaled to the decreased value of seed setting rate. Furthermore, the sucrose synthase gene RSUS2 was identified as a target of OsmiR5519 via RNA ligase-mediated 3'-amplification of cDNA ends (3'-RLM-RACE), dual luciferase assays and transient expression assays. In summary, our results suggest that OsmiR5519 regulates grain size and weight and down-regulates RSUS2 in rice. © 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.

Citation

Shengyuan Guo, Yajuan Li, Yan Wang, Yangwen Xu, Yuting Li, Ping Wu, Jinwen Wu, Lan Wang, Xiangdong Liu, Zhixiong Chen. OsmiR5519 regulates grain size and weight and down-regulates sucrose synthase gene RSUS2 in rice (Oryza sativa L.). Planta. 2024 Mar 30;259(5):106