[Show abstract][Hide abstract] ABSTRACT: Temperature has a profound effect on plant growth and development. However, the molecular mechanisms underlying this regulation are not well understood. In particular, how moderate temperature variations are perceived and transduced inside the plant cells remains obscure. In this study, we analyzed transcriptional responses to a moderate decrease in temperature (cooling) in Arabidopsis thaliana. The cooling response involves a weaker and more transient induction of cold-induced genes, such as COR15a, than cold response. This induction probably accounts for the increase in freezing tolerance by cooling acclimation. Cooling also induces some defense response genes, and their induction, but not that of COR15a, requires the salicylic acid signaling pathway. Analysis of the regulation of COR15a reveals that cooling induction is mediated through the same C repeat/dehydration-responsive (CRT/DRE) element as cold induction. Furthermore, we identified a role for CBF1 and CBF4 in transducing signals of moderate decreases in temperature. It appears that variants of the CBF signaling cascade are utilized in cold and cooling responses, and a moderate decrease in temperature may invoke an adaptive response to prepare plants to cope with a more drastic decrease in temperature.
Full-text · Article · Jul 2009 · The Plant Journal
[Show abstract][Hide abstract] ABSTRACT: Plant-pathogen interactions are known to be affected by environmental factors including temperature; however, the temperature effects have not been systematically studied in plant disease resistance. Here, we characterized the effects of a moderate increase in temperature on resistance to bacterial pathogen Pseudomonas syringae and two viral elicitors in Arabidopsis thaliana and Nicotiana benthamiana. Both the basal and the resistance (R) gene-mediated defense responses to Pseudomonas syringae are found to be inhibited by a moderately high temperature, and hypersensitive responses induced by R genes against two viruses are also reduced by an increase of temperature. These indicate that temperature modulation of defense responses to biotrophic and hemibiotrophic pathogens might be a general phenomenon. We further investigated the roles of two small signaling molecules, salicylic acid and jasmonic acid, as well as two defense regulators, EDS1 and PAD4, in this temperature modulation. These components, though modulated by temperature or involved in temperature regulation or both, are not themselves determinants of temperature sensitivity in the defense responses analyzed. The inhibition of plant defense response by a moderately high temperature may thus be mediated by other defense signaling components or a combination of multiple factors.
Full-text · Article · Jun 2009 · Molecular Plant-Microbe Interactions