The link between heat-induced polypeptides and chilling tolerance in mangoes (Mangifera indica L.), with evidence from the same fruit partially heated

Both 55degreesC hot water and 38degreesC hot air-treatments induced chilling tolerance in mango fruits. While 3 or 5 min of hot-water treatment (HWT) at 55degreesC induced chilling tolerance in mangoes, at least 12 It of hot-air treatment (HAT) at 38degreesC was needed to achieve similar results. Partial exposure of mango fruits to 55degreesC HWT for 5 min induced partial tolerance to chilling injury. As a result, the fruit was divided into two parts with striking contrast on the skin surface: the heated part was normally ripened and the unheated part was covered by typical chilling injury symptoms. To obtain direct evidence for the connection between heat-induced polypeptides and chilling tolerance, the authors made a special treatment in which one half of the mango was immersed in 55degreesC hot water for 5 min, with the other half remaining out of water in the meantime. The two-dimensional gel electrophoresis of the boiling-soluble protein fraction extracted separately from the two halves of the same mango fruit showed that three new polypeptides, with molecular weights of 13.7, 15.7 and 15.7 kD, respectively, were accumulated in the heated half and that two of them share the same molecular weights and isoelectric points with two of the three new polypeptides found in the fruits exposed for 24 h to hot air at 38degreesC. These facts showed that the two common new polypeptides were involved in some way in heat-inducted chilling tolerance in mangoes. However, whether these polypeptides are so called heat-shock proteins remains to be determined.