Yamagishi Masumi, Sakai Moeko
Research Faculty of Agriculture, Graduate School of Agriculture, Hokkaido University, Sapporo, Japan.
Front Plant Sci. 2020 Oct 30;11:590791. doi: 10.3389/fpls.2020.590791. eCollection 2020.
Some Asiatic hybrid lily cultivars develop bicolor tepals, which consist of anthocyanin-pigmented upper halves and un-pigmented lower halves. , a subgroup 6 member of R2R3-MYB that positively regulates anthocyanin biosynthesis, is downregulated in the lower halves. However, is usually expressed over entire tepal regions in numerous lily cultivars. Why of bicolor cultivars exhibits variable expression spatially in a single tepal remains unclear. Since the lily mRNA harbored a binding site for microRNA828 (miR828), the involvement of miR828 in variable spatial accumulation of transcripts was evaluated. We analyzed the cleavage of mRNA, mature miR828 accumulation, and transcript-derived siRNA generation (microRNA-seq). In the bicolor tepals, mature miR828 was more highly accumulated in the lower halves than in the upper halves, and miR828-directed cleavage of transcripts was observed predominantly in the lower halves. Moreover, the cleavage triggered the production of secondary siRNA from transcripts, and the siRNAs were accumulated predominantly in the lower halves. Consequently, miR828 suppressed transcript accumulation in the white region, and the miR828/MYB12 module participated in the development of bicolor patterns in lily flowers. The results present the first example of a microRNA mediating flower color patterns. Finally, we discuss the potential of miR828 creating flower color variations through suppressing the activity of subgroup 6 R2R3-MYB positive regulators in other species.
一些亚洲杂种百合品种会形成双色花被片，其由花青素色素沉着的上半部分和无色素沉着的下半部分组成。R2R3-MYB亚组6成员MYB12正向调控花青素生物合成，在花被片下半部分表达下调。然而，MYB12通常在许多百合品种的整个花被片区域表达。双色品种的MYB12为何在单个花被片中呈现空间可变表达仍不清楚。由于百合MYB12 mRNA含有microRNA828（miR828）的结合位点，因此评估了miR828在MYB12转录本可变空间积累中的作用。我们分析了MYB12 mRNA的切割、成熟miR828的积累以及MYB12转录本衍生的siRNA生成（小RNA测序）。在双色花被片中，成熟miR828在下半部分比在上半部分积累得更高，并且主要在下半部分观察到miR828介导的MYB12转录本切割。此外，切割触发了MYB12转录本产生次级siRNA，并且siRNA主要在下半部分积累。因此，miR828抑制了白色区域中MYB12转录本的积累，并且miR828/MYB12模块参与了百合花双色模式的形成。这些结果展示了microRNA介导花色模式的首个实例。最后，我们讨论了miR828通过抑制其他物种中R2R3-MYB亚组6正向调控因子的活性来产生花色变异的潜力。
