| China is the largest country in the citrus planting area.At present,the planting of citrus in China is mainly under the condition of open field and natural cultivation.However,the mature period of citrus produced by this kind of cultivation method is often concentrated,it makes the selling price of citrus lower,which seriously affects the income of citrus farmers.Therefore,adjusting the specific season of citrus fruits in order to ensure the quality and yield of citrus fruits can greatly increase the market price of citrus so as to create greater economic benefits.Based on this,this paper takes Wenzhou Satsuma as the raw material and takes the high quality cultivation of citrus in Xingan area of Jiangxi Province as the cut-in point,the changes of soluble solids,sugar content,acid content and sugar-acid ratio of Satsuma Mandarin in greenhouse were studied in order to understand the changes of fruit quality.At the same time,the changes of gene expression affecting sugar synthesis and citric acid synthesis and decomposition in leaves,pericarp,capsule and pulp were measured,to explore the expression of sugar and acid related genes and the molecular mechanism of synthesis and decomposition of sugar and acid in early maturing Satsuma Mandarin(Satsuma Mandarin).The findings are as follows:1.The solid and soluble sugar content of the fruits in the fully ripe cultivation increased continuously,and reached the highest level before picking,while the total acid and citric acid content decreased continuously,and the sugar-acid ratio increased all the time,so the taste of the fruit is better than that of the open-field cultivation.2.The relative expression levels of carbohydrate synthesis related genes SPS1,SPS2,SUS1,Sus3,SUS4 and SUS6 showed that the expression levels of SPS1 and SPS2 genes in leaves,pericarp and pericarp were not significantly changed,therefore,sugar accumulation in fruit does not play a major role,but increased significantly in the pulp expression.In addition,SUS3 and SUS4 increased significantly in citrus leaves,which may play a major role in sugar accumulation,while SUS4 increased significantly in pericarp,which plays a major role in sugar synthesis;The SUS1,SUS4 and SUS6 genes in the capsule increased significantly,which indicated that they played a key role in the accumulation of sugar in the capsule,and the expression of 5 genes involved in sugar synthesis in the pulp increased significantly,the results suggested that the activity of sugar synthesis in pulp might be stronger than that in other tissues and organs.3.The expression of citric acid synthesis genes PEPC and CS in four tissues and organs did not decrease but increased rapidly with time,however,the genes ACO3,GAD4 and GS2 involved in the degradation of citric acid increased to some extent in leaves,skins,meat and clothing,but the accumulation of citric acid in fruits decreased rather than increased,the results showed that the degradation activity of citric acid was much higher than that of its synthetic activity.In addition,the pathway of citric acid degradation is different in different tissues and organs.The degradation of citric acid by Gaba pathway and L-Glutamine pathway is higher in leaves,but L-Glutamine pathway is more dominant in pericarp and capsule,the pulp,on the other hand,contains more citric acid,which is degraded by the Gaba pathway.In this study,we studied the changes of sugar and acid accumulation in the fruit of Satsuma Mandarin,and the expression of related genes,the relationship between sugar acid accumulation and expression of related genes was preliminarily elucidated,which has theoretical significance for improving the quality of Satsuma Mandarin and improving the molecular mechanism of fruit quality formation. |
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