GASA5, a regulator of flowering time and stem growth in Arabidopsis thaliana

• DOI: 10.1007/s11103-009-9452-7
• Publication Date: 2009-02-03T17:48:43Z
• Authors: Shengchun Zhang; Chengwei Yang; Jianzong Peng; Shulan Sun; Xiaojing Wang
• Keywords: 0301 basic medicine; 0303 health sciences; Time Factors; Plant Stems; Arabidopsis Proteins; Reverse Transcriptase Polymerase Chain Reaction; Gene Expression Profiling; Recombinant Fusion Proteins; Green Fluorescent Proteins; Arabidopsis; Gene Expression Regulation, Developmental; Flowers; Plants, Genetically Modified; Gibberellins; 03 medical and health sciences; Plant Growth Regulators; Gene Expression Regulation, Plant; Mutation; Glucuronidase

Flowering is a critical event in the life cycle of plants and is regulated by a combination of endogenous controls and environmental cues. In the present work, we provide clear genetic evidence that GASA5, a GASA family gene in Arabidopsis (Arabidopsis thaliana), is involved in controlling flowering time and stem growth. GASA5 expression was present in all tissues of Arabidopsis plants, as detected by RT-PCR, and robust GUS staining was observed in the shoot apex of 8-day-old seedlings and inflorescence meristems during reproductive development. Phenotypic analysis showed that a GASA5 null mutant (gasa5-1) flowered earlier than wild type with a faster stem growth rate under both long-day (LD) and short-day (SD) photoperiods. In contrast, transgenic plants overexpressing GASA5 demonstrated delayed flowering, with a slower stem growth rate compared to wild-type plants. However, neither the GASA5 null mutants nor the GASA5 overexpressing plants revealed obvious differences in flowering time upon treatment with gibberellic acid (GA(3)), indicating that GASA5 is involved in gibberellin (GA)-promoted flowering. GAI (GA INSENSITIVE), one of the five DELLAs in Arabidopsis, was more highly expressed in GASA5-overexpressing plants, but it was lower in gasa5-1. Further transcript profiling analysis suggested that GASA5 delayed flowering by enhancing FLOWERING LOCUS C (FLC) expression and repressing the expression of key flowering-time genes, FLOWERING LOCUS T (FT) and LEAFY (LFY). Our results suggest that GASA5 is a negative regulator of GA-induced flowering and stem growth.