Proteomics approach reveals mechanism underlying susceptibility of loquat fruit to sunburn during color changing period

•Fifty-five differential proteins of loquat peels under heat stress were identified.•Increased anaerobic respiration may contribute to sunburn of loquat fruit peels.•Lower ability of loquat peels to scavenge ROS increases susceptibility to sunburn.•Enhanced photorespiration may result in loquats more vulnerable to sunburn.•Decreased defense pathogen proteins may increase susceptibility of fruits to sunburn. The objective of this work was to investigate why loquat fruit peels are more sensitive to high temperature and strong sunlight, making them highly susceptible to sunburn, during the color changing period (CCP). Two dimensional gel electrophoresis (2-DE) of the fruit peel proteins was performed over three developmental periods, namely green fruit period (GFP), color changing period and yellow ripening period (YRP). Fifty-five protein spots with at least 2-fold differences in abundance were successfully identified by MALDI-TOF–TOF/MS. The identified proteins were divided into categories related to heat-shock response, stress response and defense, energy metabolism, photosynthesis and protein biosynthesis. The results showed that expression of proteins related to anaerobic respiration and photorespiration were increased while the proteins related to ROS scavenging, polyamine biosynthesis, defense pathogens and photosynthesis were decreased during CCP under heat stress. Our findings provide new insights into the molecular mechanism of loquat fruit susceptible to sunburn during CCP.