Angiosperm Flora of India

XAP5 CIRCADIAN TIMEKEEPER Regulates Ethylene Responses in Aerial Tissues of Arabidopsis

Publication Type:Journal Article
Year of Publication:2011
Authors:Ellison, CT, Vandenbussche, F, Van Der Straeten, D, Harmer, SL
Journal:Plant Physiology
Date Published:2011
ISBN Number:00320889

The phytohormone ethylene differentially regulates plant architecture and growth in both a light-and nutrient-dependent fashion. The modulation of plant development by ethylene in response to both external and internal signals can also generate tissue-specific differential responses. Here, we report that XAP5 CIRCADIAN TIMEKEEPER (XCT) is involved in blue lightdependent ethylene responses in the aerial tissues of Arabidopsis (Arabidopsis thaliana) seedlings. XCT was first identified as a circadian clock mutant with a short free-running period. The xct mutation also causes sugar-specific hypocotyl growth defects, in which mutants are short in blue light when grown on a sucrose-rich medium but tall when grown on sucrose-deficient medium. Our data suggest that the hypocotyl defects in blue light are not directly caused by defects in clock or light signaling but rather by enhanced ethylene responses. In blue light, xct mutants have a more active ethylene response pathway and exhibit growth phenotypes similar to the constitutive ethylene signaling mutant constitutive triple responsel (ctrl). xct mutants also have reduced ethylene emission, analogous to plants that have lost CTR1 function. Genetic analysis suggests that XCT negatively regulates ethylene responses downstream of ETHYLENE-INSENSITIVE3 in aerial tissues. However, XCT is not required for all ethylene-mediated processes, such as the inhibition of root growth. Thus, XCT acts downstream of a major transcriptional regulator in an organ-specific manner, playing an environment-dependent role in the regulation of plant growth.

Short Title:Plant Physiology
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Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith