Discovering genetic factors influencing cereal endosperm starch by exploiting natural variation in Aegilops tauschii

McNelly, Rose (2024) Discovering genetic factors influencing cereal endosperm starch by exploiting natural variation in Aegilops tauschii. Doctoral thesis, University of East Anglia.

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Abstract

Cereal endosperm starch is of great social and commercial importance, providing up to 50% of dietary calories globally, whilst also being used to produce paper and biodegradable polymers. Triticeae (e.g., wheat, barley and rye) grains have two types of starch granules: large lenticular A-type granules and small spherical B-type granules. Starch granule size distribution and composition influences nutritional and functional quality, but the mechanisms determining these remain poorly understood.

Here I aimed to discover genetic factors influencing starch granule size distributions in the Triticeae using natural variation in Aegilops tauschii, the wheat D-genome progenitor. I discovered significant variation in starch granule size distributions within a diversity panel of 117 Ae. tauschii accessions, which exceeded that observed in domesticated wheat. I exploited this variation in a genome wide association study, identifying ten novel genomic loci associated with B-type granules. By utilising publicly available datasets and bioinformatic predictions, I identified 13 gene candidates within these loci that might influence B-type granule formation. Interestingly, one of these encodes for Limit Dextrinase (LDA), a starch debranching enzyme. I discovered two LDA variants with increased enzymatic activity which are prevalent in Ae. tauschii accessions with large B-type granules. However, complete elimination of LDA in tetraploid wheat caused only minor effects on endosperm starch granules. Together, this suggests that gain-of-function mutations in LDA influence B-type granule formation, perhaps by affecting malto-oligosaccharide metabolism.

My work highlights the potential of Ae. tauschii to discover novel variation and new gene candidates involved in starch granule formation in the Triticeae, and reveals a role for LDA in influencing variation in starch granule traits. Further characterisation of the novel gene candidates will extend our mechanistic understanding of A-type and B-type granule formation. Furthermore, the loci could be integrated into breeding programs to improve grain quality by modulating starch granule size.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Science > School of Biological Sciences
Depositing User:	Chris White
Date Deposited:	09 Jan 2025 09:33
Last Modified:	09 Jan 2025 09:33
URI:	https://ueaeprints.uea.ac.uk/id/eprint/98128
DOI:

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