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

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 'Flort16A' 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 'Flort16A' . In addition, 'Flort16A' had a higher content of lutein, zeaxanthin and beta-carotene, whereas 'Jinshi 1' had specific beta-cryptoxanthin on ripening, accordingly, the expression of CHYB1, which encodes the enzyme for the formation of zeaxanthin and beta-cryptoxanthin, was higher during the last developmental stage in 'Jinshi 1' than in 'Flort16A'. These results suggested that the higher carotenoid/chlorophyll ratio, as well as the higher beta-cryptoxanthin proportion are the important reasons for the brighter yellow flesh color.

Automated summary

The biochemical and molecular factors causing flesh-color variation between two yellow-flesh kiwifruit cultivars were identified by analyzing carotenoids, chlorophyll composition, and gene expression profile during fruit development. The brighter yellow flesh of 'Jinshi 1' was attributed to higher carotenoid/chlorophyll ratio and beta-cryptoxanthin proportion, along with differences in gene expression related to chlorophyll degradation and carotenoid formation.