The Study Of Lycopene Biosynthesis Key Gene Expression And Related Hormone In Polyploidy Watermelon(Citrullus Lanatus)

In this study, three different groups watermelon cultivar including their diploid(2X), triploid(3X)and tetraploid(4X) were researched, including L1(zhong9, red flesh), L2(Mimei, red flesh) andL3(Huangmei, yellow flesh). In order to analysis the relations between watermelon fruit lycopeneaccumulation and biosynthesis genes expression in different ploidy and flesh color, the contents of fruitlycopene during watermelon development as well as the expression of five key genes (phytoenesynthase PSY, phytoene desaturase PDS, ζ-carotene desaturase ZDS, carotenoid isomerase CRTISO,lycopene-β-cyclase LCYb) were measured. In the same time, the expression differences was analysisedin different ploidy roots, stems, leaves of ‘Mimei’ watermelon. These will be provided the foundationfor the study of watermelon carotenoid accumulation during the whole growth period in different ploidy.Then compared hormones difference in different ploidy, we will provide evidence for polyploidwatermelon and high lycopene contents breeding. The main results are as follows:1. Lycopene accumulation of watermelon fruits in different ploidy and color watermelon:In this research, there were significant differents about the content of lycopene in different varietiesand different ploidy, lycopene content of tetraploid and triploid watermelon fruit is greater thandiploid in the whole period. In the late fruit development, lycopene content in red watermelon fruit wastriploid>tetraploid>diploid. However, the content of lycopene in the different ploidy watermelon fruitwith lemon yellow are at a very low level in the whole period.2. Lycopene biosynthsis genes expression difference of watermelon with different ploidy and color:The expression trend of genes are characterized by "increase-decrease-increase-decrease ", the bothpeaks values were at15d and25d after pollination. The PSY gene expression difference in differentploidy was tetraploid> triploid> diploid at15d and25d after pollination. In all of five genes, theexpression of PSY is the highest among the whole growth period. The expression of LCYb in red fleshwatermelon was the lowest in all genes, especially at25d after pollination, while its expression in theyellow flesh watermelon just below the PSY, this suggests the importance of LCYb in color control andlycopene synthesis.The expression of PDS, ZDS, CRTISO also had certain differences in different development period,but the difference was not obvious, the overall trend was ‘increase-decrease’. In all of five genes, onlyCRTISO in red flesh was higher expression than yellow flesh watermelon throughout the whole preiod.And in red flesh watermelon, the erpression of CRTISO was higher in diploid than polyploidy,but itsexpression was higher in polyploidy than diploid. Its effect in watermelon flesh color decided was alsocrucial.For the root, stem and leaf, the highest expression of all five genes were almost appeared onflowering satge. And only the PSY expression in diploid was higher than polyploidy, the expression ofother genes in diploid were lower than polyploidy.3.The change of endogenous hormone content in different ploidy watermelon:The contents of five endogenous hormones including IAA, ABA, GA, ZR and BR are measured in different ploidy ‘Mimei’ watermelon fruit, the result shows that there were two peaks about the contentof IAA in different ploidy watermelon fruit, but the time when peaks appear was different in differentploidy; the content of ABA was increased in later development, but there was a bigger variation trend indifferent ploidy, The content of GA gradually decreased in three different ploidy, the content of ZR kepta certain level during the whole development periods in different ploidy, but there was a peak at25dafter pollination; while the content of BR was very low, kept5-20ng·g-1·Fw during the wholedevelopment periods. The contents of endogenous hormones in root, stem and leaf were measured, theresult shows that the highest content of every endogenous hormone was appeared at flower or matureperiod, there was no obvious regularity about the content of hormones in different ploidy varieties.4.The correlation between endogenous hormones accumulation and lycopene synthesisThe same substrate was shared both GA and lycopene, the content of GA was showed the trend of‘increase-decrease’ in the whole period, this was the negatively correlation with the lycopene; ABAsynthesis was the continuation of the lycopene synthesis, there was the consistent between ABA andlycopene synthesis in diploid watermelon. There was no correlation between other hormones andlycopene.