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Tomato plants increase their tolerance to low temperature in a chilling acclimation process entailing comprehensive transcriptional and metabolic adjustments.

Low temperature is a major environmental stress that seriously compromises plant development, distribution and productivity. Most crops are from tropical origin and, consequently, chilling sensitive. Interestingly, however, some tropical plants, are able to augment their chilling tolerance when previously exposed to suboptimal growth temperatures. Yet, the molecular and physiological mechanisms underlying this adaptive process, termed chilling acclimation, still remain practically unknown. Here, we demonstrate that tomato plants can develop a chilling acclimation response, which includes comprehensive transcriptomic and metabolic adjustments leading to increased chilling tolerance. More important, our results reveal strong resemblances between this response and cold acclimation, the process whereby plants from temperate regions raise their freezing tolerance after exposure to low, non-freezing temperatures. Both chilling and cold acclimation are regulated by a similar set of transcription factors and hormones, and share common defence mechanisms, including the accumulation of compatible solutes, the mobilization of antioxidant systems and the rearrangement of the photosynthetic machinery. Nonetheless, we have found some important divergences that may account for the freezing sensitivity of tomato plants. The data reported in this manuscript should foster new research into the chilling acclimation response with the aim of improving tomato tolerance to low temperature.