Low‐temperature perception leading to gene expression and cold tolerance in higher plants

Summary Plant species exhibit a range of tolerances to low temperatures, and these constitute a major determinant of their geographical distribution and use as crops. When tolerance is insufficient, either chilling or freezing injuries result. A variety of mechanisms are employed to evade the ravages of extreme or sub‐optimal temperatures. Many of these involve cold‐responsive gene expression and require that the drop in temperature is first sensed by the plant. Despite intensive research over the last 100 yr or longer, we still cannot easily answer the question of how plants sense low temperature. Over recent years, genomic and post‐genomic approaches have produced a wealth of information relating to the sequence of events leading from cold perception to appropriate and useful responses. However, there are also crucial and significant gaps in the pathways constructed from these data. We describe the literature pertaining to the current understanding of cold perception, signalling and regulation of low‐temperature‐responsive gene expression in higher plants, raising some of the key questions that still intrigue plant biologists today and that could be targets for future work. Our review focuses on the control of gene expression in the pathways leading from cold perception to chilling and freezing tolerance. Contents Summary 737 I. Chilling and freezing: two different stresses requiring different solutions 738 II. Identification of a major cis ‐element in the control of cold gene expression 739 III. The CBF transcription factors (TFs) and their regulation 739 IV. Events downstream of CBFs 740 V. A post‐genomic view on global transcript changes in response to low temperature 741 VI. The effect of light and circadian signals on cold gene expression 742 VII. Post‐transcriptional regulation 742 VIII. A receptor for cold? 742 IX. What are the characteristics of plant cell thermometer(s)? 744 X. Low‐temperature signalling downstream of perception 744 XI. Unresolved questions 747 Acknowledgements 748 References 748