Main conclusion

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.

Abstract

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.

中文翻译：

---

OsmiR5519 调节水稻 (Oryza sativa L.) 中的籽粒大小和重量并下调蔗糖合酶基因 RSUS2

主要结论

OsmiR5519的上调导致籽粒大小、重量和结实率下降。OsmiR5519在籽粒灌浆过程中发挥重要作用，并下调蔗糖合酶基因RSUS2。

抽象的

MicroRNA (miRNA) 是一类小型非编码 RNA，是植物生长和发育的关键调节因子。在水稻中，保守的 miRNA 被发现可以调节产量成分，但水稻特异性 miRNA 的功能却很少被研究。人们发现水稻特有的OsmiR5519在生殖发育过程中大量表达，但其生物学作用仍不清楚。在本研究中，通过 miR5519 过表达系 ( miR5519-OE ) 和 miR5519 沉默系 ( STTM5519 )来表征水稻特异性OsmiR5519的功能。苗期miR5519 -OE品系叶片中蔗糖、葡萄糖和果糖含量明显低于野生型(WT)品系。与 WT 水稻相比，miR5519-OE品系的籽粒大小和重量显着降低。 miR5519-OE中的外壳细胞宽度小于 WT 中的外壳细胞宽度。miR5519-OE品系的结实率显着降低，但STTM5519品系则没有。细胞学观察表明，籽粒灌浆不足是miR5519-OE品系结实率下降的主要原因。miR5519-OE品系籽粒缺陷率达40% ，几乎与结实率下降值相当。此外，通过RNA连接酶介导的cDNA末端3'-扩增(3'-RLM-RACE)、双荧光素酶测定和瞬时表达测定，蔗糖合酶基因RSUS2被鉴定为OsmiR5519的靶标。总之，我们的结果表明OsmiR5519调节水稻的籽粒大小和重量并下调RSUS2。