Liu Nian, Tu Lili, Wang Lichen, Hu Haiyan, Xu Jiao, Zhang Xianlong
National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, Hubei, 430070, China.
BMC Plant Biol. 2017 Jan 10;17(1):7. doi: 10.1186/s12870-016-0969-z.
microRNAs (miRNAs) have been involved in regulation of diverse spectrum of plant development processes in many species. In cotton, few miRNAs have been well characterised in floral organ development. Floral organ, which should be finely tuned, is a crucial factor affecting the yield of cotton. Therefore, it is well worth revealing the function of miRNAs in regulation of floral organ development. Here, we report the role of miRNA156/157 in regulation of floral organ size in cotton.
Over-expression of the GhmiRNA157 precursor in cotton (Gossypium hirsutum) resulted in smaller floral organs, fewer ovules and decreased seed production due to suppression of cell proliferation and cell elongation. Five SQUAMOSA promoter-binding protein-like (SPL) genes were identified as targets of GhmiRNA157 using a RNA ligase-mediated rapid amplification of cDNA end approach, and the expression level of miR157-targeted GhSPLs decreased in the miR157 over-expression lines, indicating the presence of the miR157/SPL axis in cotton. Two MADS-box genes, orthologs of AtAGL6 and SITDR8, which are associated with floral organ development and reproductive production, were repressed in the miR157 over-expression lines. In addition, auxin-inducible genes were also down-regulated, and auxin signal visualized by a DR5::GUS reporter was attenuated in the miR157 over-expression lines.
Our results indicate that the miR157/SPL axis controls floral organ growth and ovule production by regulating MADS-box genes and auxin signal transduction. The work further elucidates the mechanism of floral organ development and provides helpful molecular basis for improvement of cotton yield.
微小RNA（miRNA）参与了许多物种中多种植物发育过程的调控。在棉花中，很少有miRNA在花器官发育方面得到充分表征。花器官是影响棉花产量的关键因素，其发育需要精细调控。因此，揭示miRNA在调控花器官发育中的功能非常值得。在此，我们报道了miRNA156/157在调控棉花花器官大小中的作用。
在棉花（陆地棉）中过表达GhmiRNA157前体导致花器官变小、胚珠数量减少以及种子产量下降，这是由于细胞增殖和细胞伸长受到抑制。使用RNA连接酶介导的cDNA末端快速扩增方法，鉴定出5个SQUAMOSA启动子结合蛋白样（SPL）基因作为GhmiRNA157的靶标，在miR157过表达系中，miR157靶向的GhSPLs的表达水平降低，表明棉花中存在miR157/SPL轴。两个与花器官发育和生殖生产相关的MADS-box基因，即AtAGL6和SITDR8的直系同源基因，在miR157过表达系中受到抑制。此外，生长素诱导基因也下调，并且在miR157过表达系中，由DR5::GUS报告基因可视化的生长素信号减弱。
我们的数据表明，miR157/SPL轴通过调控MADS-box基因和生长素信号转导来控制花器官生长和胚珠产生。这项工作进一步阐明了花器官发育的机制，并为提高棉花产量提供了有用的分子基础。
