National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, the Chinese Academy of Sciences, Shanghai, China.
J Integr Plant Biol. 2011 Jun;53(6):480-92. doi: 10.1111/j.1744-7909.2011.01050.x.
Floral initiation is a major step in the life cycle of plants, which is influenced by photoperiod, temperature, and phytohormones, such as gibberellins (GAs). It is known that GAs promote floral initiation under short-day light conditions (SDs) by regulating the floral meristem-identity gene LEAFY (LFY) and the flowering-time gene SUPPRESSOR OF OVEREXPRESSION OF CO 1 (SOC1). We have defined the role of the auxin signaling component INDOLE-3-ACETIC ACID 7 (IAA7)/AUXIN RESISTANT 2 (AXR2) in the regulation of flowering time in Arabidopsis thaliana. We demonstrate that the gain-of-function mutant of IAA7/AXR2, axr2-1, flowers late under SDs. The exogenous application of GAs rescued the late flowering phenotype of axr2-1 plants. The expression of the GA20 oxidase (GA20ox) genes, GA20ox1 and GA20ox2, was reduced in axr2-1 plants, and the levels of both LFY and SOC1 transcripts were reduced in axr2-1 mutants under SDs. Furthermore, the overexpression of SOC1 or LFY in axr2-1 mutants rescued the late flowering phenotype under SDs. Our results suggest that IAA7/AXR2 might act to inhibit the timing of floral transition under SDs, at least in part, by negatively regulating the expressions of the GA20ox1 and GA20ox2 genes.
花的起始是植物生命周期中的一个重要步骤，它受光周期、温度和植物激素（如赤霉素（GA））的影响。已知 GA 通过调节花分生组织-身份基因 LEAFY（LFY）和开花时间基因 SUPPRESSOR OF OVEREXPRESSION OF CO1（SOC1），在短日照条件（SDs）下促进花的起始。我们已经确定了生长素信号成分 INDOLE-3-ACETIC ACID 7（IAA7）/AUXIN RESISTANT 2（AXR2）在拟南芥开花时间调节中的作用。我们证明，IAA7/AXR2 的功能获得突变体 axr2-1 在 SDs 下开花较晚。GA 的外源应用挽救了 axr2-1 植物的晚花表型。GA20 氧化酶（GA20ox）基因 GA20ox1 和 GA20ox2 的表达在 axr2-1 植物中降低，并且在 SDs 下，axr2-1 突变体中 LFY 和 SOC1 转录本的水平降低。此外，在 axr2-1 突变体中过表达 SOC1 或 LFY 挽救了 SDs 下的晚花表型。我们的结果表明，IAA7/AXR2 可能通过负调控 GA20ox1 和 GA20ox2 基因的表达，来抑制 SDs 下花转变的时间，至少部分是这样。
