Ambient temperature and gibberellins in plant development

Plants are sessile organisms and have to respond to changes in their environment flexibly. One of the major factors that influence plant growth and development is ambient temperature, yet surprisingly little is known about mechanisms of temperature perception and the signal transduction pathways that trigger the observed responses. In many processes, phytohormones are involved in the integration of environmental signals into plant development. Gibberellins are one group of phytohormones regulating key developmental processes that are also influenced by environmental conditions, such as seed dormancy and germination, plant growth and flowering. Gibberellin biosynthesis and catabolism are highly regulated and temperature might play an important role in modulating levels of this hormone, as enzymes involved in gibberellin catabolism are specifically induced by low temperature. Transcripitional regulation of gibberellin responses is mediated by DELLA proteins, a family of negative regulators that are controlled by the level of bioactive gibberellins. Significantly, the phenotype of plants grown at low temperature is largely absent in DELLA knockout lines, suggesting that DELLA proteins may be involved in the cold response via gibberellin signalling pathways. The present project application aims to investigate the interaction of low temperature, gibberellins and DELLA proteins in modulating plant growth. The analysis of plant lines obtained by screening mutagenized reporter lines for altered temperature responses will identify signalling components that modulate gibberellin catabolism in a temperature responsive manner. Furthermore, an extensive microarray study will be performed to identify DELLA targets on transcriptional level and investigate the role of DELLA proteins in temperature response. Regulation of the identified DELLA targets will be further analysed biochemically using chromatin immunoprecipitation. A meta-analysis of data obtained from these experiments should identify global targets regulated by DELLA proteins and temperature. The response to ambient temperature is an important process during plant development and the experiments proposed in this application will improve our understanding how temperature modulates plant growth.