Characterising and engineering diversity for wheat carotenoid biofortification

Waites, Joshua Oliver (2024) Characterising and engineering diversity for wheat carotenoid biofortification. Doctoral thesis, University of East Anglia.

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Plant carotenoids play roles in photosynthesis, photoprotection, phytohormone
production, pigmentation, and also contribute to human health as essential components of
a healthy diet. In wheat, active grain carotenoid biosynthesis is responsible for the yellow
colour of flour, an important quality trait in durum wheat breeding. This thesis aimed to
explore and engineer the genetic diversity of wheat grain carotenoid content (GCC), thus
contributing towards the development of wheat with advantageous GCC traits.

Using spectrophotometric and HPLC analyses, I measured the GCC diversity of 443 Watkins
global landrace accessions from both tetraploid and hexaploid collections. I found
considerable variation, including some accessions with very high GCC. These results
represent the largest high-resolution analysis of GCC within wheat diversity. Next, I
identified 15 marker-trait associations and 14 quantitative trait loci (QTLs) associated with
grain carotenoid traits within the Watkins tetraploid collection. Eleven of these were novel
QTLs for carotenoid traits and may represent diversity unique to this collection.

Additionally, I examined the role of the ORANGE gene in wheat. This gene influences
carotenoid biosynthesis in other plants but had not been characterised in wheat before.
Using EMS mutants, I found that knocking out ORANGE reduced GCC, thereby confirming
its role in carotenoid biosynthesis in wheat. Next, I showed that overexpressing a variant of
ORANGE, containing a polymorphism known to significantly increase carotenoid
accumulation in melons, resulted in higher GCC in wheat than the overexpression of the
wild-type gene. This demonstrated for the first time that the polymorphism could enhance
GCC in a cereal crop. Finally, I attempted to engineer variation within endogenous ORANGE
using gene editing strategies to increase GCC in wheat. While this was unsuccessful, I
identified an ORANGE EMS mutant line with increased GCC. Excitingly, this could be a novel
gain-of-function mutation within ORANGE that increases carotenoid accumulation.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Zoe White
Date Deposited: 09 Jul 2024 15:28
Last Modified: 09 Jul 2024 15:28

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