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23929720
Abscisic acid regulates axillary bud outgrowth responses to the ratio of red to far-red light.

Plant Physiol, 2013/10;163(2):1047-58.

Reddy SK[1], Holalu SV, Casal JJ, Finlayson SA

Affiliations

PMID: 23929720DOI: 10.1104/pp.113.221895

Impact factor: 8.005

Abstract
Low red light/far-red light ratio (R:FR) serves as an indicator of impending competition and has been demonstrated to suppress branch development. The regulation of Arabidopsis (Arabidopsis thaliana) rosette bud outgrowth by the R:FR and the associated mechanisms were investigated at several levels. Growth under low R:FR suppressed outgrowth of the third from topmost bud (bud n-2) but not that of the topmost bud. Subsequently increasing the R:FR near the time of anthesis promoted bud n-2 outgrowth and reduced topmost bud growth. Buds from specific rosette positions, exhibiting divergent fates to increased R:FR, were harvested 3 h after modifying the R:FR and were used to conduct ATH1 microarray-based transcriptome profiling. Differentially expressed genes showed enrichment of light signaling and hormone-related Gene Ontology terms and promoter motifs, most notably those associated with abscisic acid (ABA). Genes associated with ABA biosynthesis, including the key biosynthetic gene NINE-CIS-EPOXYCAROTENOID DIOXYGENASE3 (NCED3), and with ABA signaling were expressed at higher levels in the responsive bud n-2, and increasing the R:FR decreased their expression only in bud n-2. ABA abundance in responsive buds decreased within 12 h of increasing the R:FR, while indole-3-acetic acid levels did not change. A role for ABA in repressing bud outgrowth from lower positions under low R:FR was demonstrated using the nced3-2 and aba2-1 ABA biosynthesis mutants, which showed enhanced branching and a defective bud n-2 outgrowth response to low R:FR. The results provide evidence that ABA regulates bud outgrowth responses to the R:FR and thus extend the known hormonal pathways associated with the regulation of branching and shade avoidance.
MeSH terms
Abscisic Acid; Arabidopsis; Arabidopsis Proteins; Biosynthetic Pathways; Ecotype; Flowers; Gene Expression Profiling; Gene Expression Regulation, Plant; Gene Ontology; Genes, Plant; Indoleacetic Acids; Light; Light Signal Transduction; Phenotype
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