Mutant combinations of lycopene ɛ-cyclase and β-carotene hydroxylase 2 homoeologs increased β-carotene accumulation in endosperm of tetraploid wheat (Triticum turgidum L.) grains.

Abstract

Grains of tetraploid wheat (Triticum turgidum L.) mainly accumulate the non-provitamin A carotenoid lutein-with low natural variation in provitamin A β-carotene in wheat accessions necessitating alternative strategies for provitamin A biofortification. Lycopene ɛ-cyclase (LCYe) and β-carotene hydroxylase (HYD) function in diverting carbons from β-carotene to lutein biosynthesis and catalyzing the turnover of β-carotene to xanthophylls, respectively. However, the contribution of LCYe and HYD gene homoeologs to carotenoid metabolism and how they can be manipulated to increase β-carotene in tetraploid wheat endosperm (flour) is currently unclear. We isolated loss-of-function Targeting Induced Local Lesions in Genomes (TILLING) mutants of LCYe and HYD2 homoeologs and generated higher order mutant combinations of lcye-A, lcye-B, hyd-A2, and hyd-B2. Hyd-A2 hyd-B2, lcye-A hyd-A2 hyd-B2, lcye-B hyd-A2 hyd-B2, and lcye-A lcye-B hyd-A2 hyd-B2 achieved significantly increased β-carotene in endosperm, with lcye-A hyd-A2 hyd-B2 exhibiting comparable photosynthetic performance and light response to control plants. Comparative analysis of carotenoid profiles suggests that eliminating HYD2 homoeologs is sufficient to prevent β-carotene conversion to xanthophylls in the endosperm without compromising xanthophyll production in leaves, and that β-carotene and its derived xanthophylls are likely subject to differential catalysis mechanisms in vegetative tissues and grains. Carotenoid and gene expression analyses also suggest that the very low LCYe-B expression in endosperm is adequate for lutein production in the absence of LCYe-A. These results demonstrate the success of provitamin A biofortification using TILLING mutants while also providing a roadmap for guiding a gene editing-based approach in hexaploid wheat.

• Authors: Shu Yu, Michelle Li, Jorge Dubcovsky, Li Tian
• Journal: Plant biotechnology journal (Plant Biotechnol J) Vol. 20 Issue 3 Pg. 564-576 (03 2022) ISSN: 1467-7652 [Electronic] England
• PMID: 34695292 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © 2021 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.

Chemical References

• Provitamins
• Xanthophylls
• beta Carotene
• Carotenoids
• Mixed Function Oxygenases
• beta-carotene hydroxylase
• Intramolecular Lyases
• lycopene cyclase-isomerase
• Lycopene
• Lutein

Topics

• Anodontia
• Carotenoids (metabolism)
• Endosperm (genetics, metabolism)
• Intramolecular Lyases (genetics, metabolism)
• Lutein (metabolism)
• Lycopene (metabolism)
• Mixed Function Oxygenases (genetics, metabolism)
• Provitamins (metabolism)
• Tetraploidy
• Triticum (genetics, metabolism)
• Xanthophylls (metabolism)
• beta Carotene (genetics, metabolism)