Metabolic engineering of ???2?￠????carotene in orange fruit increases its in vivo antioxidant properties

摘要

Orange is a major crop and an important source of health?￠????promoting bioactive compounds. Increasing the levels of specific antioxidants in orange fruit through metabolic engineering could strengthen the fruit's health benefits. In this work, we have afforded enhancing the ???2?￠????carotene content of orange fruit through blocking by RNA interference the expression of an endogenous ???2?￠????carotene hydroxylase gene ( Cs???2?￠????CHX ) that is involved in the conversion of ???2?￠????carotene into xanthophylls. Additionally, we have simultaneously overexpressed a key regulator gene of flowering transition, the FLOWERING LOCUS T from sweet orange ( CsFT ), in the transgenic juvenile plants, which allowed us to obtain fruit in an extremely short period of time. Silencing the Cs???2?￠????CHX gene resulted in oranges with a deep yellow (?￠????golden?￠????) phenotype and significant increases (up to 36?￠????fold) in ???2?￠????carotene content in the pulp. The capacity of ???2?￠????carotene?￠????enriched oranges for protection against oxidative stress in vivo was assessed using Caenorhabditis elegans as experimental animal model. Golden oranges induced a 20% higher antioxidant effect than the isogenic control. This is the first example of the successful metabolic engineering of the ???2?￠????carotene content (or the content of any other phytonutrient) in oranges and demonstrates the potential of genetic engineering for the nutritional enhancement of fruit tree crops.