| Fruit texture has a significant impact on its taste,storage,transportation and shelf life.Texture are formed during fruit ripening in which along with a variety of biochemical processes and molecular regulation mechanisms.The varieties of melon are very rich,and the texture of different melons are different.But the important biological processes that affect the texture of melon fruit are still not clear.In this study,some physiological and biochemical processes and transcriptome sequencing data of different texture melon during ripening were analyzed in order to elucidate some factors that might affect the texture of melon fruit.The main results were as follows:1.The cell morphology changes of melon fruit with different tastes during ripening were observed by paraffin section method.The results showed that significant or highly significant positive correlations were found between cell size parameters(cell area,perimeter,length and width)and adhesiveness(0.951* ~ 0.983**).Cell area was found to exert a significant negative influence on TPA hardness and crispness(-0.910* and-0.926*,respectively),and cell length and width also had a significant influence on crispness(-0.884* and-0.894*,respectively),indicating that the melon fruit will had harder texture with smaller flesh cells.In the cell shape parameters,the correlation between cell roundness and adhesiveness was also significant(0.936*).2.The contents of cell wall components(pectin,cellulose and hemicellulose)and enzymes activity of melon fruit with different tastes during ripening were analyzed.The results showed that water-soluble pectin and ionic-soluble pectin were increased during fruit ripening,chelate-soluble pectin,cellulose and hemicellulose showed a downward trend;the contents of cell wall components in melon fruits with different tastes were different.The changes of different cell wall enzymes activity were different,and their activities of melon fruit were also different.The relationships between fruit hardness and cell wall compositions as well as that between fruit hardness and enzymes activity in ripe fruits showed that TPA hardness,adhesiveness and crispness were significantly correlated with cellulose content(0.788*,-0.886** and 0.863*,respectively).Texture parameters were also significantly correlated with cellulase activity(0.838*~0.940**),indicating that cellulose and its degrading enzyme activity played a key role in the texture of melon flesh.3.Transcriptome sequencing data of two melons P10 and 417 with different tastes during ripening were analyzed.Most of the genes that may be involed in fruit texture were related to cell wall,such as high expression of polygalacturonase,pectinesterase and ?-galactosidase genes can break down cell wall;and galacturonosyltransferase,XTH protein and cellulase synthetase genes contributed to the stability of cell wall structure.Some genes that coding calcium-binding protein,aquaporin and cell wall structure protein may also contributed to cell wall structure.In addition,some genes related to plant hormones,such as ethylene synthesis enzyme gene ACO1 and MYB,bHLH and WRKY transcription factors may also have a role in melon texture.4.Seven xyloglucan endotransglycosylase/hydrolase(XTH)proteins and their expression in fruit during ripening and plant organs(root,stem,leaf and flower)of P10,417 and Charentais were analyzed.The results showed that MELO3C014468,MELO3C026755,MELO3C017481 and MELO3C017478 may have xyloglucan endotransglucosylase enzyme activity which may contribute to the enhancement of cell wall structure.MELO3C026755 gene may play an important role in fruit texture.The other genes MELO3C003441,MELO3C005245 and MELO3C018292 may have both xyloglucan endotransglucosylase and endohydrolase enzyme activities,in which MELO3C003441 may play a very important role in the texture of melon fruit. |
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