Study On HXK Molecular Mechanism In The Regulation Of Loquat Sugar Accumulation

Loquats originate in China with long history of cultivation. Loquat fruits, shaped like Apricots,taste sweet, soft and juicy, with sweet flavor and delicate flesh. Loquats, riching in various nutrientsneeded by the body, are nutritional healthy fruits. However, the majority of our loquat fruits have lowsugar content, lighter flavor, resulting in greater impact on the quality of loquats. The sugar content isone of the important indicators of fruit quality, also the basic raw material for the synthesis of acid,carotenoids and other nutrients and aromatic substances. Sugar content directly affects the consumptionvalue and commodity value of fruits. Therefore, the research of sugar accumulation physiology andmolecular mechanisms of loquat fruits can clarify fruit sugar regulation mechanism, and provide thetheoretical basis for improving the quality of loquat fruits. This study used adult loquat tree(Eriobotryajaponica (Thunb.) Lindl.) in Zhejiang Agriculture and Forestry University Botanical Gardenas materials. Clone hexokinase gene to study it’s expression patterns during development of loquatfruits and the changes in the relationship between hexokinase activity and fruit sugar content. Theresults were as follows:Get full-length cDNA sequences of Hexokinase gene by RACE technology separation, whichshowed that the total length of hexokinase gene was1839bp, the length of5’-UTR was59bp, the lengthof3’-UTR was291bp, the length of ORF was1491bp, encoding497amino acids. The full-length cDNAsequences of loquats had homology of72%-81%with other plants, such as orange, grape. Analyze thehexokinase gene expression of loquat leaves, mature leaves, stems, flowers and loquat fruit at differentdevelopmental stages by Real-Time RT-PCR. Hexokinase gene had higher expression level in loquatflower tissues; while during fruits development, it had low expression level30days after flowering, thenincreased rapidly to the maximum75days after flowering, and reduced slowly until fruits ripening.CaMV35S as a promoter of the GFP protein, connect ORFEjHXK1to the upstream side of theGFP coding region of pCAMBIA-1302dual vector, use a gene gun, to transform the recombinantplasmid into onion epidermal cells, and then observe under confocal microscopy of GFP signal.Confocal imaging of GFP fluorescence shows that the GFP fluorescence fusion protein of35S: EjHXK1is primarily in the cell membrane.Three kinds of sugar content are measured in the process of loquatfruit development by HPLC method.In the prophase of the entire development process, the loquat fruitsugar was mainly sucrose. With the increase in the maturity, sucrose content was gradually reduced, butthe change was relatively stable. In the prophase of fruit ripening, the glucose and fructose content werelower, both increased75days after flowering with the fruit maturing, and reached to the highest in fruitripening. The total sugar level was the highest in the mature fruits. In early fruit development, the loquatfruit hexokinase activity maintained a higher level, and then decreased gradually.