Journal
JOURNAL OF INTEGRATIVE PLANT BIOLOGY
Volume 53, Issue 6, Pages 480-492Publisher
WILEY-BLACKWELL
DOI: 10.1111/j.1744-7909.2011.01050.x
Keywords
Arabidopsis; GA 20-oxidases; GAs; IAA7/AXR2; auxin
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Funding
- National Natural Science Foundation of China [90917014]
- Ministry of Science and Technology of China [2006AA10A102]
- National Special Grant for Transgenic Crops [2009ZX08009-081B]
- Science and Technology Commission of Shanghai Municipality [10XD1402300]
- Shanghai Leading Academic Discipline Project [B209]
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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.
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