植物科学研究权威期刊Plant Cell于7月9日在线发表植生生态所植物分子遗传国家重点实验室陈晓亚研究组最新研究成果： miR156－靶基因SPL调控拟南芥表皮毛的分布。
植物表皮毛覆盖于植物地上组织的表面，具有多种不同的生理功能，有些还具有重要的经济价值，如棉纤维。表皮毛的分布受到时空调控。模式植物拟南芥在营养发育时期，表皮毛主要生长于莲座叶的近轴面；而当植物进入生殖发育期，表皮毛的数量随着花序轴的延伸而减少，直至花器官（除花萼外）基本无毛。这一分布特征表明表皮毛发育的调控与植物发育的时相转换有着密不可分的关系。
SPL (SQUMOSA PROMOTER BINDING PROTEIN LIKE)基因编码重要的转录因子。SPL家族的大部分成员是microRNA156的靶基因，它们在植物进入生殖生长期的时相转换过程中起关键的调控作用。过量表达miR156 (p35S::MIR156f)导致SPLs水平降低，花序轴上部和花柄器官均出现异位毛生长；反之SPL基因高表达导致茎杆上表皮毛数量下降甚至光滑无毛。在拟南芥表皮毛发育过程中，GL1-GL3-TTG1蛋白复合体正调控表皮毛发育，而棉纤维发育也由类似复合体控制。另一类单MYB转录因子TRICHOMELESS 1 (TCL1) 和TRIPTYCHON (TRY)在蛋白水平上与GL1竞争结合GL3，从而阻断表皮毛发育。研究表明，SPL9通过直接结合TCL1和TRY的启动子来激活这两个负调控因子，抑制表皮毛生长。上述结果表明，受miR156调控的SPLs基因家族是连接植物发育进程和表皮毛发育的桥梁。棉花植物中miR156的含量很高，其对棉纤维发育的调控作用值得进一步探讨。
该项工作得到了国家科技部、国家自然科学基金委、中国科学院的经费支持。(生物谷Bioon.net)
生物谷推荐原文出处：
Plant Cell doi：10.1105/tpc.109.072579
Temporal Control of Trichome Distribution by MicroRNA156-Targeted SPL Genes in Arabidopsis thaliana
Nan Yua,b,1, Wen-Juan Caia,b,1, Shucai Wangc, Chun-Min Shana,b, Ling-Jian Wanga and Xiao-Ya Chena,2
a National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, 200032 Shanghai, P.R. China
b Graduate School of Chinese Academy of Sciences, 200032 Shanghai, P.R. China
c Department of Botany, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
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.
