MicroRNAs (miRNAs) are known to play critical roles in regulating rice agronomic traits through mRNA cleavage or translational repression. Our previous study indicated that miR5504 regulates plant height by affecting cell proliferation and expansion. Here, the two independent homozygous mir5504 mutants (CR1 and CR2) and overexpression lines (OE1 and OE2) were further used to investigate the functions of miR5504. The panicle length, 1000-grain weight and grain yield per plant of miR5504-OE lines were identical to those of Nipponbare (NIP), but the 1000-grain weight of mir5504 mutants was reduced by about 10% and 9%, respectively. Meanwhile, the grain width and thickness of mir5504 mutants decreased significantly by approximately 10% and 11%, respectively. Moreover, the cytological results revealed a significant decrease in cell number along grain width direction and cell width in spikelet in mir5504, compared with those in NIP. In addition, several major storage substances of the rice seeds were measured. Compared to NIP, the amylose content of the mir5504 seeds was noticeably decreased, leading to an increase of nearly 10 mm in gel consistency (GC) in mir5504 lines. Further investigation confirmed that LOC_Os08g16914 was the genuine target of miR5504: LOC_Os08g16914 over-expression plants phenocopied the mir5504 mutants. This study provides insights into the role of miR5504 in rice seed development.

中文翻译：

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miR5504 对水稻株高、产量和品质的多效性影响

已知 MicroRNA (miRNA) 通过 mRNA 裂解或翻译抑制在调节水稻农艺性状中发挥关键作用。我们之前的研究表明miR5504通过影响细胞增殖和扩张来调节植物高度。在这里，两个独立的纯合mir5504突变体（CR1和CR2）和过表达系（OE1和OE2）被进一步用于研究miR5504的功能。miR5504-OE品系的穗长、千粒重和单株籽粒产量与日本晴(NIP)相同，但mir5504突变体的千粒重分别减少了约10%和9%。同时，mir5504突变体的晶粒宽度和厚度分别显着减少约10%和11%。此外，细胞学结果显示，与NIP相比，mir5504中沿粒宽方向的细胞数量和小穗细胞宽度显着减少。此外，还测量了水稻种子的几种主要储存物质。与 NIP 相比，mir5504 种子的直链淀粉含量显着降低，导致 mir5504 品系的凝胶稠度 (GC) 增加了近 10 mm。进一步研究证实LOC_Os08g16914是miR5504的真正靶标：LOC_Os08g16914过表达植物表现出mir5504突变体的表型。这项研究深入了解了 miR5504 在水稻种子发育中的作用。