XAP5 CIRCADIAN TIMEKEEPER regulates ethylene responses in aerial tissues of Arabidopsis

Department of Plant Biology, College of Biological Sciences, University of California, Davis, California 95616, USA.
Plant physiology (Impact Factor: 6.84). 02/2011; 155(2):988-99. DOI: 10.1104/pp.110.164277
Source: PubMed


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 light-dependent 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 response1 (ctr1). 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.

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Available from: Filip Vandenbussche, Mar 19, 2014
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    • "e to ethylene emissions . Ethylene signaling components , such as EIN3 , also display a similar oscil - latory pattern of expression in response to light and sugar availability ( Yanagisawa et al . , 2003 ; Lee et al . , 2006 ) . XAP5 CIRCADIAN TIMEKEEPER ( XCT ) is also involved in blue light - dependent ethylene responses in Arabidopsis shoots ( Ellison et al . , 2011 ) . The expression of ABA - and JA - responsive genes also oscil - lates diurnally ( Mizuno and Yamashino , 2008 ) . The genes impli - cated in the synthesis of geranylgeranyl diphosphate ( GGDP ) , an intermediate metabolite in isoprenoids synthesis , which leads to the production of chlorophylls , carotenoids , tocopherols , ABA and G"
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    • "At2g21150 encodes a nuclear localized protein, XCT, that is highly conserved across species (Martin-Tryon and Harmer, 2008). XCT was first isolated from a genetic screen for mutants with altered circadian clock running (Martin-Tryon and Harmer, 2008) and later shown to be involved in ethylene signaling (Ellison et al., 2011). "
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