The contribution of biotechnology to improving post-harvest chilling tolerance in fruits and vegetables using heat-shock proteins

Fresh fruits and vegetables have a short post-harvest life and are prone to post-harvest losses due to mechanical injury, physiological causes and decay. Low-temperature storage is widely used as post-harvest treatment applied for delaying senescence in vegetables and ornamentals and ripening in fruits, upholding their post-harvest quality. But the refrigerated storage of tropical and subtropical crop plant species provokes a set of physiological alterations known as chilling injury that negatively affect their quality and frequently renders the product not saleable. Membrane damage and reactive oxygen species (ROS) accumulation are the main adverse effects of chilling injury impact in sensitive horticultural products. The chilling injury tolerance of certain plant species is attributed to their ability to accumulate heat-shock proteins (HSP). The beneficial action of HSP in chilling tolerance is due to their chaperone activity but, besides this biological function, small HSP (sHSP) are able to function as membrane stabilizers and ROS scavengers, or synergistically with cell antioxidant systems. Also, biosynthesis of osmolytes such as raffinose and proline is under the regulation of heat-shock transcription factors (HSTF). These molecules are critical for osmotic adjustment since low temperatures also provoke a secondary osmotic stress. The use of biotechnological strategies can be envisaged, with the aim of generating engineered crop plants of horticultural interest to induce the production and action of HSP and HSTF, in order to assure the beneficial effects of these proteins in promoting chilling injury tolerance during their post-harvest refrigerated storage. In particular, induction of HSTF expression using biotechnology has significant potential and interest for reducing the impact of chilling injury on sensitive produce, avoiding the practical difficulties of applying the classic post-harvest technologies based on heat treatment.