Expression Analysis Of LCYB Gene In Watermelon Accessions With Different Flesh Color

Watermelon is a kind of gourd,dicotyledonous plants and origins from Africa.Watermelon is a sweety and juicy common fruits in summer,containing an abundant of nutrients such as carbohydrates,mineral salts,multiple vitamins and also amino acids(citrulline,arginine and glutathione)which are good for cardiovascular and cerebrovascular.Watermelon is rich in lycopene which is beneficial for human body.Lycopene can prevent people away from causing cancer and imporve skin beautifly,skin care and other health functions.The lycopene P-cyclase gene(LCYB)is able to convert lycopene into β-carotene.The formation of the flesh color in watermelon was controlled by multiple genes.The relationship between LCYB gene and the formation of watermelon flesh color was valuble for further investigation.The purpose of this study was to validate the function of LCYB gene which has influenced the flesh color formation of watermelon,analysing the structure of LCYB gene in 7 accessions with different flesh color(red,yellow,pink and white).The pigment accumulation was measured through the high performance liquid chromatography to detect the protein expression of LCYB.The lycopene content of flesh in seven watermelon varieties from friuit setting to mature during the five development stages and the expression of LCYB was also tested by the technology of fluorescence quantitative PCR(qPCR).The relationship between LCYB gene and the formation of watermelon flesh color was discussed based on the aspects of gene level,transcription level and protein level.The following conclusions are obtained through this research:There are three different SNP mutant sites of LCYB sequences among seven experimental watermelon materials which located on the 11th,675th,and 1305th bases in the gene sequence.Two non-synonymous SNPs(675th and 1305th positions for the gene sequences)are found in the protein sequences(225th and 435th posotions for the protein sequences).The two 225th loci of protein sequences could distinguish the difference between watermelon materials which are rich in lycopene(red and pink flesh)and other flesh color watermelon materials.The 435th loci of protein sequences could distinguish the yellow flesh watermelon accessions away from other flesh color watermelon materials(red,pink,orange and white).The results of high performance liquid chromatography among seven watermelon materials at different fruit developmental stages showed that the white pulp watermelon material ZXG0000 could not detected any pigments through the whole growth period.Abundant of lycopene and fewβ-carotene were detected in red flesh watermelon accessions ZXG55,ZXG79,ZXG1549 and pink flesh accessions ZXG1452 and ZXG1594.However,a large number of beta carotene was detected in yellow flesh materials ZXG77.Low gene expression was detected in red flesh watermelon materials ZXG55,ZXG79 and ZXG1549 during fruit ripening and the gene expression was not high in pink fleshed materials ZXG1452 and ZXG1594 during the fruit ripening period.The LCYB gene expression of white flesh watermelon ZXG0000 maintained high expression through the fruit setting and maturation;during the stages of fruit mature,the gene expression of yellow fleshed ZXG77 was slightly higher than other developmental stages.The expression level of LCYB gene can affect the synthesis of lycopene,thereby affect the formation of watermelon flesh color,however,the LCYB gene is not the only factor that affecting the flesh color formation which controlled by multiple genes.The protein expression level of LCYB gene is not significant difference among white fleshed ZXG0000,red fleshed ZXG55,ZXG55,ZXG79,ZXG1549,pink fleshed ZXG1452,ZXG1594 and yellow fleshed ZXG77 according to results of the enzyme activity test.