Abstract
Ethylene induces enhanced differential growth in petioles of Arabidopsis (Arabidopsis thaliana), resulting in an upward movement of the leaf blades (hyponastic growth). The amplitude of this effect differs between accessions, with Columbia-0 (Col-0) showing a large response, while in Landsberg erecta (Ler), hyponastic growth is minimal. Abscisic acid (ABA) was found to act as an inhibitory factor of this response in both accessions, but the relationship between ethylene and ABA differed between the two; the ability of ABA to inhibit ethylene-induced hyponasty was significantly more pronounced in Col-0. Mutations in ABI1 or ABI3 induced a strong ethylene-regulated hyponastic growth in the less responsive accession Ler, while the response was abolished in the ABA-hypersensitive era1 in Col-0. Modifications in ABA levels altered petiole angles in the absence of applied ethylene, indicating that ABA influences petiole angles also independently from ethylene. A model is proposed whereby the negative effect of ABA on hyponastic growth is overcome by ethylene in Col-0 but not in Ler. However, when ABA signaling is artificially released in Ler, this regulatory mechanism is bypassed, resulting in a strong hyponastic response in this accession.
Highlights
Abscisic acid (ABA) influences many aspects of plant growth and development, ranging from seed desiccation to acclimation to environmental stresses (Zeevaart and Creelman, 1988)
We focus on the role of ABA in the regulation of initial petiole angles and ethylene-induced hyponastic growth in Arabidopsis and whether the observed difference in hyponastic response between accessions could be explained by a different relationship between ethylene and ABA
We investigated whether ABA influenced ethylene-induced hyponastic growth in Arabidopsis petioles, and whether the different responses of Col-0 and Landsberg erecta (Ler) could be contributed to a different interaction between the two hormones
Summary
Abscisic acid (ABA) influences many aspects of plant growth and development, ranging from seed desiccation to acclimation to environmental stresses (Zeevaart and Creelman, 1988). Progress has been made in the characterization of ABA signal transduction pathways, the signal transduction pathways, including the receptor, are not yet fully understood. Recent work by Razem et al (2006) identified the late flowering RNA-binding protein FCA as a receptor for ABA, but the function of this protein seems to be related to some specific processes only, such as lateral root formation and flowering. Over 50 loci that affect ABA responsiveness were identified (reviewed in Finkelstein et al, 2002; Himmelbach et al, 2003). ABA response mutants were identified in screens for altered sensitivity to ABA during germination. Many mutations affecting ABA response were identified in screens for alterations in other signalling pathways (for example sugar sensing, Huijser et al, 2000)
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