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Effect of ploidy level on expression of lycopene biosynthesis genes and accumulation of phytohormones during watermelon (Citrullus lanatus) fruit growth and ripening

发布日期:2017/9/18 10:07:47 浏览次数: 来源:中国无籽西瓜网  

Effect of ploidy level on expression of lycopene biosynthesis genes and accumulation of phytohormones during watermelon (Citrullus lanatus) fruit growth and ripening

DOU Jun-linga,b, YUAN Ping-lia, ZHAO Sheng-jiea, HE Nana, ZHU Hong-jua,b, GAO Leia, JI Wan-lia, LU Xu-qianga,*, LIU Wen-gea,*

a Zhengzhou Fruit Research Institute, Chinese Academy of Agricultural Sciences, Zhengzhou 450009, China

b College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan 430070, China

 

Abstract

We studied the difference of lycopene and phytohormone levels among diploid, triploid and tetraploid plants of two watermelon cultivars during fruit growth and ripening. The expression pattern of five genes (PSY1, PDS, ZDS, CRTISO and LCYB) was analyzed in details. In red-fleshed cultivar ‘MIMEI’, lycopene content increased rapidly from 25 to 35 DAP (day after pollination), and then decreased at 40 DAP. Triploid and tetraploid fruit had higher levels of lycopene than diploid. Moreover, triploid tended to contain more lycopene than tetraploid during fruit growth and ripening stages. However, little lycopene content in yellow-fleshed cultivar ‘HUANGMEI’ was found during all fruit development stages being tested. In ‘MIMEI’, transcript level of PSY1 was generally higher than the other four genes, and LCYB gene expression was the lowest among all five genes being tested. PSY1, CRTISO and LCYB genes showed higher transcript levels in polyploid than in diploid fruit. By contrast, in ‘HUAGMEI’, transcript level of LCYB was not the lowest, but only lower than PSY1. PSY1, CRTISO and LCYB genes showed higher expression levels in diploid than in polyploid fruit. In ‘MIMEI’, the negative correlation between GA content and lycopene accumulation was determined in all three different ploidy fruit, while a positive correlation was observed between ABA content and lycopene accumulation only in diploid watermelon. These results indicated that the lycopene content in watermelon is regulated by the differential transcription expression of the lycopene metabolic genes and phytohormones.

Keywords: watermelon, lycopene, gene expression, ploidy, flesh color, phytohormone