Biochemical and molecular factors governing flesh-color development in two yellow-fleshed kiwifruit cultivars

Abstract

To identify the biochemical and molecular factors causing flesh-color variation between two yellow-flesh kiwifruit cultivars 'Jinshi 1′ and 'Jinyan', the composition of carotenoids and chlorophyll, and associated gene expression profile in their pulp were investigated during fruit development. At harvest, ‘Jinshi 1′ exhibited brighter yellow flesh than ‘Hort16A’ with a lower color hue angle, although they had a similar total carotenoid content. At the molecular level, ‘Jinshi 1′ exhibited higher expression level of chlorophyll catabolic genes (CBR, PPH, and PAO), leading to lower accumulation of chlorophyll in the flesh. Meanwhile, higher expression levels of NCED1 resulted in greater carotenoid degradation in ‘Hort16A’. In addition, ‘Hort16A’ had a higher content of lutein, zeaxanthin and β-carotene, whereas ‘Jinshi 1′ had specific β-cryptoxanthin on ripening, accordingly, the expression of CHYB1, which encodes the enzyme for the formation of zeaxanthin and β-cryptoxanthin, was higher during the last developmental stage in ‘Jinshi 1′ than in ‘Hort16A’. These results suggested that the higher carotenoid/chlorophyll ratio, as well as the higher β-cryptoxanthin proportion are the important reasons for the brighter yellow flesh color.