Red light-transmittance bagging promotes carotenoid accumulation through xanthophylls esterification during the ripening of blood orange fruit

Citrus fruit is a carotenoid and vitamin-rich food. Here, we investigated the effects of red, blue, and white light-transmittance bagging (LTB) on carotenoid (Car) metabolism during 'Moro' blood orange ripening. A total of 50 carotenoids were identified, and phytoene and violaxanthins were predominant in the pulp, accounting for over 82.12 % of total Cars. Red LTB increased the esterification of xanthophylls easily absorbed by the human body and promoted Car accumulation. The esterification of violaxanthin, lutein, β-cryptoxanthin, and zeaxanthin by caprate (C10), laurate (C12), myristate (C14), palmitic (C16), and oleate (C18) was the main contributor to the observed patterns. CsAt1g54570, a potential xanthophyll esterase, might mediate the esterification of β-cryptoxanthin. Our results shed light on the role of red LTB in enhancing Car esterification and accumulation in citrus pulp and provide a promising method for promoting Car accumulation during citrus production.