Mechanism Of Heat Treatment In Improving Chilling Tolerance Of Peach Fruit And In Silico Cloning Of A Related Phospholipase D Gene

Increasing evidences suggest that phospholipase D (PLD) is associated with low temperature stress in plant tissues. Among plant organs, peach fruit are highly susceptible to chilling injury (CI). However, little is known about the role of PLD (i.e., gene expression; protein level and activity) in postharvest chilling tolerance of peach fruit. In this work, using peach fruit (Prunus persica L. cv.jiubao) as materials, the molecular and cellular mechanism of relationship between chilling tolerance and PLD was verified by western, RT-PCR or other technologies. The main results were as follows:1. Peach fruits were pretreated at 38 oC for 48 h and then transferred to 2 oC for cold storage. Compared with the control without heat pretreatment, membrane permeability and malondialdehyde (MDA) contents were reduced in the heat-pretreated fruits under low temperature. During heat treatment, free SA was activated. Meanwhile, the PLD activity and its expression in response to heat acclimation were then assayed. The results indicated PLD was significantly activated at enzyme activity, as well as synthesis of new PLD protein during the early of heat acclimation. Thus, all these results infer that SA and PLD may be involved in the heat response, and have roles in heat pretreatment-induced chilling tolerance of harvested peach fruits. This work offers an important basis for further investigating the mechanism of post-harvest fruit adaptation to environmental stresses.2. A novel cDNA of PLDαwas isolated with BLAST search in combination with RT-PCR from peach fruit. The obtained PLDαgene contained a complete open reading frame encoding a 91.5-kDa protein of 807 amino acid residues, which possessed the characteristic C2 domain and the two catalytic HKD motifs. The alignment analysis of the deduced peach PLDαprotein with other known PLDαfamily proteins indicates that peach PLDαis conserved and highly homologous with strawberry PLDα. This work provided a scientific basis for further investigating the mechanism of post-harvest fruit adaptation to low temperature.