National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, 200032 Shanghai, PR China.
Plant Cell. 2010 Jul;22(7):2322-35. doi: 10.1105/tpc.109.072579. Epub 2010 Jul 9.
The production and distribution of plant trichomes is temporally and spatially regulated. After entering into the flowering stage, Arabidopsis thaliana plants have progressively reduced numbers of trichomes on the inflorescence stem, and the floral organs are nearly glabrous. We show here that SQUAMOSA PROMOTER BINDING PROTEIN LIKE (SPL) genes, which define an endogenous flowering pathway and are targeted by microRNA 156 (miR156), temporally control the trichome distribution during flowering. Plants overexpressing miR156 developed ectopic trichomes on the stem and floral organs. By contrast, plants with elevated levels of SPLs produced fewer trichomes. During plant development, the increase in SPL transcript levels is coordinated with the gradual loss of trichome cells on the stem. The MYB transcription factor genes TRICHOMELESS1 (TCL1) and TRIPTYCHON (TRY) are negative regulators of trichome development. We show that SPL9 directly activates TCL1 and TRY expression through binding to their promoters and that this activation is independent of GLABROUS1 (GL1). The phytohormones cytokinin and gibberellin were reported to induce trichome formation on the stem and inflorescence via the C2H2 transcription factors GIS, GIS2, and ZFP8, which promote GL1 expression. We show that the GIS-dependent pathway does not affect the regulation of TCL1 and TRY by miR156-targeted SPLs, represented by SPL9. These results demonstrate that the miR156-regulated SPLs establish a direct link between developmental programming and trichome distribution.
植物表皮毛的产生和分布受到时间和空间的调节。进入开花期后，拟南芥植物的花序茎上的表皮毛数量逐渐减少，花器官几乎无毛。我们在这里表明，SQUAMOSA PROMOTER BINDING PROTEIN LIKE (SPL) 基因，定义了一个内源性开花途径，并且是 microRNA 156 (miR156) 的靶标，在开花期间暂时控制表皮毛的分布。过表达 miR156 的植物在茎和花器官上产生了异位表皮毛。相比之下，SPL 水平升高的植物产生的表皮毛较少。在植物发育过程中，SPL 转录本水平的增加与茎上表皮毛细胞的逐渐丧失相协调。MYB 转录因子基因 TRICHOMELESS1 (TCL1) 和 TRIPTYCHON (TRY) 是表皮毛发育的负调控因子。我们表明，SPL9 通过结合其启动子直接激活 TCL1 和 TRY 的表达，并且这种激活不依赖于 GLABROUS1 (GL1)。细胞分裂素和赤霉素被报道通过 C2H2 转录因子 GIS、GIS2 和 ZFP8 诱导茎和花序上的表皮毛形成，后者促进 GL1 的表达。我们表明，GIS 依赖的途径不影响 miR156 靶向 SPLs 对 TCL1 和 TRY 的调节，以 SPL9 为例。这些结果表明，miR156 调节的 SPLs 在发育编程和表皮毛分布之间建立了直接联系。
