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: 7.39). 02/2011; 155(2):988-99. DOI: 10.1104/pp.110.164277
Source: PubMed

ABSTRACT 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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    ABSTRACT: Background In view of ethylene's critical developmental and physiological roles the gaseous hormone remains an active research topic for plant biologists. Progress has been made to understand the ethylene biosynthesis pathway and the mechanisms of perception and action. Still numerous questions need to be answered and findings to be validated. Monitoring gas production will very often complete the picture of any ethylene research topic. Therefore the search for suitable ethylene measuring methods for various plant samples either in the field, greenhouses, laboratories or storage facilities is strongly motivated.ScopeThis review presents an update of the current methods for ethylene monitoring in plants. It focuses on the three most-used methods - gas chromatography detection, electrochemical sensing and optical detection - and compares them in terms of sensitivity, selectivity, time response and price. Guidelines are provided for proper selection and application of the described sensor methodologies and some specific applications are illustrated of laser-based detector for monitoring ethylene given off by Arabidopsis thaliana upon various nutritional treatments.Conclusions Each method has its advantages and limitations. The choice for the suitable ethylene sensor needs careful consideration and is driven by the requirements for a specific application.
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