30 Arabidopsis thaliana as a Model for Studying Mechanisms of Plant Cold Tolerance

Plants vary widely in their ability to tolerate cold temperatures. Many species from tropical and subtropical regions are chilling-sensitive (Lyons 1973; Levitt 1980). Such plants suffer a wide range of damage, ranging from loss of vigor to death, when temperatures drop below about 10°C. In contrast, plants from temperate regions are not only chilling-tolerant, but many can survive freezing at high subzero temperatures (Sakai and Larcher 1987). Moreover, many chilling-tolerant plants increase in freezing tolerance in response to low nonfreezing temperature, a process known as cold acclimation (Levitt 1980; Sakai and Larcher 1987). Nonacclimated wheat and rye, for example, are killed at about −5°C, but after cold acclimation, they can survive temperatures as low as about −20°C and −30°C, respectively. A major challenge for plant scientists interested in low-temperature biology is to determine the molecular bases for plant chilling and freezing tolerance. Why are certain plants such as rice and cucumber sensitive to chilling temperatures whereas plants such as wheat and rye are not? Why is it that the common potato, Solanum tuberosum, cannot cold-acclimate although its close tuber-bearing relative, Solanum commersonii, can? What is the molecular basis for the enhancement of freezing tolerance that occurs with cold acclimation? Considerable effort has been directed toward addressing these and related questions, and much has been learned. However, our understanding of the underlying bases for chilling sensitivity and freezing tolerance remains at an elementary level. We cannot yet answer the questions posed above, for instance, or rationally design from first principles a...