Metabolic engineering of β-carotene in orange fruit increases its in vivo antioxidant properties

Plant Biotechnol J. 2014 Jan;12(1):17-27. doi: 10.1111/pbi.12112. Epub 2013 Aug 27.


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 β-carotene content of orange fruit through blocking by RNA interference the expression of an endogenous β-carotene hydroxylase gene (Csβ-CHX) that is involved in the conversion of β-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 Csβ-CHX gene resulted in oranges with a deep yellow ('golden') phenotype and significant increases (up to 36-fold) in β-carotene content in the pulp. The capacity of β-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 β-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.

Keywords: Caenorhabditis elegans; FLOWERING LOCUS T; carotenoids; citrus; genetic transformation; health.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antioxidants / metabolism
  • Citrus / metabolism*
  • Fruit / metabolism*
  • Metabolic Engineering / methods*
  • Mixed Function Oxygenases / genetics
  • Mixed Function Oxygenases / metabolism
  • Plants, Genetically Modified / metabolism*
  • beta Carotene / metabolism*


  • Antioxidants
  • beta Carotene
  • Mixed Function Oxygenases
  • beta-carotene hydroxylase