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Certain carotenoids,most importantly β-carotene,are cleaved to vitamin A within the body.Red-fleshed Ioquat(Eriobotrya japonica Lindl.)fruits are naturally rich in β-carotene when fully ripe.However,the flesh of white-fleshed cultivars accumulated very low concentrations of carotenoids during ripening.Previously,the possible reasons,focusing on the biogenesis of chromoplasts,were described at the 2011 International Workshop on Biology of Fruit Quality.Here we report the roles of phytoene synthase(PSY)gene members in carotenoid accumulation in tissues of red-and white-fleshed Ioquats.With the aid of RNA-Seq,four members,EjPSY1,EjPSY2A,EjPSY2B,and EjPSY3 were identified.These members have different expression patterns,with EjPSY1 most expressed in leaves and peel,EjPSY2A in peel and flesh,EjPSY2B in leaves,while EjPSY3 showed very low expression in any tissues.The expression patterns were quite similar between two tested cultivars,Luoyangqing(LYQ),red-fleshed,and Baisha(BS),white-fleshed.However,sequence differences were found for EjPSY2A.In BS,a mutant EjPSY2Ad,lacking the C-terminal region was proved to be nonfunctional according to a functional complementation assay.Therefore,the loss-of-function mutation of EjPSY2A well explained the lack of carotenoids in the BS flesh.This mutation is conserved in all six whitefleshed cultivars tested.In contrast to flesh,the peel and leaves of BS can accumulate carotenoids,up to 30-56%and 82-85%of LYQ,respectively.This is due to the expression of other functional PSY members,especially EjPSY1 in peel and EjPSY2B in leaves.In conclusion,a truncated and non-functional mutant EjPSY2Ad is responsible for the less accumulation of carotenoids in the flesh of white-fleshed cultivars.The tissue-specific expression of EjPSY1 and EjPSY2B well explained carotenoid accumulation in peel and leaf tissues in white-fleshed cultivars.