Protective proteins are differentially expressed in tomato genotypes differing for their tolerance to low-temperature storage.

When stored at low temperature, tomato fruits exhibit chilling injury symptoms, such as rubbery texture and irregular ripening. To identify proteins related to chilling tolerance, we compared two tomato near isogenic lines differing for their texture phenotype at harvest in a fruit-storage trial including two temperatures (4 and 20 degrees C) along several days of conservation. Fruit evolution was followed by assessing fruit color, ethylene emission and texture parameters. The most contrasted samples were submitted to proteomic analysis including two-dimensional electrophoresis and mass spectrometry of protein spots to identify the proteins, whose expression varied according to the genotype or the storage conditions. Unexpectedly, the most firm genotype at harvest was the most sensitive to cold storage. The other genotype exhibited a delay in fruit firmness loss leading to the texture differences observed after 20 days of 4 degrees C storage. The proteome analysis of these contrasted fruits identified 85 proteins whose quantities varied with temperature or genotype. As expected, cold storage decreased the expression of proteins related to maturation process, such as acidic invertase, possibly controlled post-translational regulation of polygalacturonase and up-regulated proteins related to freezing tolerance. However, the study point out proteins involved in the differential resistance to chilling conditions of the two lines. This includes specific isoforms among the large family of small heat shocked proteins, and a set of proteins involved in the defense against of the reticulum endoplasmic stress.