Abstract:

In this study，the pericarp surrounding the blossom end of normal and cracked fruits（three degrees of fruit cracking）from the‘Duwei’pummelo cultivar were used for high throughput RNA sequencing. Some differentially expressed genes are potentially associated with fruit cracking. Galacturonosyltransferase（catalyzing homogalacturonan synthesis）and arabinogalactan protein （maintaining cell wall structure）genes were significantly down-regulated，however，genes （polygalacturonase，pectate lyase）involved in the pectin degradation pathway were significantly up regulated in cracked pericarp compared to the un-cracked pericarp. The changes in the expression of these genes may link to a decrease in mechanical strength of the cell wall，consequently inducing fruit cracking. A gene for 3-ketoacyl-CoA synthase（participating long chain lipid acid synthesis）was 5-6 times in un-cracked pericarp compared to cracked pericarp，suggesting that the decrease in transcript level of the gene may lead to a lower capacity of pericarp to suppress transpiration，ultimately，may lead to water deficiency stress，cell death，and microcrack formation in pericarp. Genes related to high temperature or water deficiency（dehydration-responsive element-binding protein，calcineurin B-like-interacting protein kinase，WRKY30，WRKY33，and WRKY40）were significantly down regulated in cracked pericarp，indicating the possible association of high temperature and water deficiency with fruit cracking.

Key words: pummelo, fruit cracking, transcriptome, pectin, wax, high temperature, water deficiency