Changes Of Main Fruit Quality And Activity Of Key Enzymes In Pectin Decomposition And Their Expression In Blueberry Fruit Development Process

Blueberry is a small berry with rich nutrition and high economic value,and it has received extensive attention in recent years.In this experiment,we used three varieties of blueberry,O'Neal,Brigitta and Britewell,as the experimental materials.The compositions involved into fruit appearance quality and nutritional quality were determined.The dynamic changes of fruit PG enzyme activity,PME enzyme activity and ?-gal enzyme activities were determined.At the same time,we investigated expression of 10 genes encoding pectin decomposition enzymes in blueberry fruit from color conversion to mature.From the results,we analyzed the status of blueberry quality composition dynamic changes in different varieties,and the effects of pectin decomposing enzymes activities on fruit quality compositions.(1)During the growth and development of blueberry fruit,with the growth of single fruit weight,the fruit hardness decreased and the fruit gradually softened and matured.During the period,the content of soluble sugar increased,titratable acid content first increased and then decreased,and the overall taste became better.Vc content gradually decreased,and soluble protein content first increased,following lightly decreasing and then increasing.When the fruits being over ripe,it would further soften,got more water soluble substances and its resistance to mechanical damage got worse.(2)Within the three varieties,the size of O'Neal mature fruit was larger than the other two.The best sugar-acid rate was in Britewell fruit,better than that of O'Neal,and Brigitta showed lowest sugar-acid rate.Followed by O'Neal,the soluble protein was the highest in Brigitta,and Britewell showed the lowest content of soluble protein.In over ripe fuits,O'Neal showed the highest content of Vc,followed by Britewell and then Brigitta.Generally,Britewell showed the best quality from both the appearance and nutritional contents,followed by O'Neal and Brigitta.Whereas,because Britewell is a kind of rabbiteye blueberry,its thick pericarp and seeds large lead to less commodity value for direct fresh than O'Neal.(3)PG enzyme activity increased significantly during fruit color conversion,and it was negatively correlated with fruit firmness changes,which illustrated that the activity of PG enzyme promoted fruit softening.PG enzyme catalyzes water soluble pectin decomposition,which results in the increase of soluble sugar content.?-Gal activity was higher in both young fruit stage and fruit maturation period,which showed that ?-gal activity was not only related with fruit ripening,also with fruit swelling.The activity of PME changed little in the process of fruit development.In general,PG and ?-gal played important roles in the process of blueberry fruit softening.(4)The PG enzyme activity was possibly regulated by PG(3)gene expression,and as the same time,PG(1)and PG(2)genes would put part effects on PME enzyme activity.The ?-gal enzyme activity might be primarily regulated by ?-gal16 gene expression.The expressions and ?-gal1 and ?-gal3 should be negligible.The regulation on PME enzyme activity would be more complicated.The expression of PE3 would be due to integrated expression of several PME genes,and PE,PE31 and PME3 were the possible genes serving pivotal roles.