Identification And Analysis Of Sugar Components And SPS And SPP Family Genes In Mango Fruit

Mangifera indica L.is commonly known as mango,Anacardiaceae evergreen tree,which is the second largest tropical fruit in the world next to bananas.Mango fruit has rich flavor and remarkable sweetness.Sweet fruit flavor is an important factor affecting fruit flavor,and the sweet taste of mango fruit is mainly determined by sugar content.There is a great difference in sweet taste among different varieties.However,there is little research on the molecular basis for the difference of sweet taste of different varieties.In this experiment,three different cultivars with different sweetness（’Guifei’,’Tumang’,’Baixiangya’）were selected as test materials.The physiological indexes of fructose content（sucrose,glucose,fructose）in mango were determined,and related genes of sucrose metabolism were excavated with genomic data.The expression patterns of sucrose synthesis key family genes and their evolutionary relationships in plants were analyzed.Then the correlation between sucrose content and the expression of sucrose synthesis key family genes was further analyzed.The role of SPS and SPP family genes in sucrose synthesis was identified by theexperiments.The main findings are as follows:1.The sugar contents in flesh of three mango varieties’ Guifei’,Tumango’ and’Baixiangya’ were analyzed.The content of sucrose,glucose and fructose from mango fruits was determined by HPLC in the mature green and full ripening stage.The results show that among the three mature species,the sucrose content was the highest,the fructose content was the second,and the glucose content was the lowest.For different varieties,the highest sucrose content was ’Guifei’,.The highest content of fructose was Tumang’.The highest glucose content was ’Baixiangya’.During the ripening of the fruit,the sucrose content in ’Guifei’ and ’Baixiangya’ fruits increased significantly,the next one is fructose,while glucose content showed a downward trend.The content of three sugars in ’Tumang’all showed an increasing trend,among which fructose content increased the largest.The content of sucrose,total sugar and sweetness increased most from green stage to full ripening in ’Guifei’ cultivar,which is the highest at full ripening stage.2.Sucrose synthesis related enzymes（SPS and SPP）and sucrose metabolism related enzymes（VIN,CWIN and CIN）were analyzed based on Mango genome data mining.Firstly,The results of protein domain identification showed that proteins encoded by SPS and SPP have one same domain,S6PP,and the proteins encoded by VIN and CWIN have the same two conserved domains,Glyco_hydro₃2N and Glyco_hydro₃2C.Secondly,including two SPS genes named SPS1 and SPS2,and three SPP genes named SPP1,SPP2 and SPP3.respectively.Then,phylogenetic tree results revealed that SPS and SPP genes evolved from advanced plants.The proteins encoded by SPS and SPP genes in mango fruit were closely related to orange.3.The expression levels of SPS and SPP family genes in flesh and peel of three mango cultivars were analyzed.The results displayed that the expression levels of SPS gene were higher in ’Tumang’,’Baixiangya’ was the lowest.The SPS2 gene has a higher gene expression level in the peel and flesh of ’Tumang’,while the SPS1 gene has a lower expression level in the peel and flesh of ’Baixiangya’.The expression level of SPP family genes was highest in the flesh of ’Tumang’,and the expression level of ’Guifei’ was the lowest.In addition,the expression level of ’Guifei’ was highest in the peel,and the expression level of ’Baixiangya’ was the lowest.The expression of SPP3 gene was highest in the flesh of ’Tumang’,while the expression of SPP2 gene was highest in the peel of’Guifei’.It can be preliminarily concluded from the qRT-PCR data that the SPS2 gene of the SPS family gene and the SPP3,SPP2 gene of the SPP family gene play a decisive role in the peel and flesh of sucrose synthesis pathway.4.The sucrose content in the flesh of ’Guifei’ and ’Baixiangya’increased first and then decreased,which consistent with the change of SPP1,SPP2 and SPP3 genes in the post-ripening process.and the highest sucrose content and expression was observed at 96 h after ethylene treatment.The results showed that there was a significant positive correlation between the sucrose content and the relative expression of SPS2,SPP1,SPP2 and SPP3 genes in the flesh of ’Guifei’ and ’Baixiangya’.The highest sucrose content and gene expression were found in the flesh of ’Tumang’ with ethylene treatment for 144 h.There was a significant positive correlation between the sucrose content and the relative expression of SPS1 genes in the flesh of Tumang’.The results showed that the contents of sucrose,glucose and fructose in different mango cultivars were significantly different.The sweetness of mango fruit was’ Guifei’,’Tumango’ and ’white ivory’ from high to low,respectively.Two SPS genes and three SPP genes can be obtained by gene mining.The SPS2 gene of SPS family gene and the SPP3,SPP2 gene of SPP family gene play an important role in sucrose accumulation and sweet taste formation in mango fruit.