Early Events During Low Temperature Signaling

Environmental factors, such as temperature and water availability, are important determinants of plant growth, development and geographical distribution. Thus crop production is severely limited by stresses due to freezing temperatures and drought. The vulnerability of plants to environmental stresses is primarily due to their sessile growth habit. However, the same growth habit, by enforcing a selection pressure, has also led to the development of sophisticated mechanisms by which plants constantly monitor their environment and activate mechanisms to tolerate these stresses. Plants incapable of mounting such responses succumb to the stressful environment. Thus, freezing tolerant plants can survive sub-zero temperatures for months. They do so by sensing the non-lethal initial decline in temperature as seen in nature at the onset of winter and launching the processes involved in cold acclimation. Cold acclimation is a complex process comprising perception of non-freezing low temperature, transmission of this perception to the nucleus through a cascade of transduction events, and activation of gene transcription; products resulting from this step then confer freezing tolerance on the plant. Cold acclimation is a time-dependent process, the completion of which may take days or weeks. The state of acclimation temporally coincides with the stress and as the latter is relieved, de-acclimation occurs rapidly. Therefore, in order to improve crop production, and to extend geographical range of crop growth, a clear understanding of the processes involved in cold acclimation is essential.