Cereal asparagine synthetase genes

A - Papers appearing in refereed journals

Raffan, S. and Halford, N. G. 2020. Cereal asparagine synthetase genes. Annals of Applied Biology - AAB. https://doi.org/10.1111/aab.12632

AuthorsRaffan, S. and Halford, N. G.

Asparagine synthetase catalyses the transfer of an amino group from glutamine to aspartate to form glutamate and asparagine. The accumulation of free (non-protein) asparagine in crops has implications for food safety because free asparagine is the precursor for acrylamide, a carcinogenic contaminant that forms during high-temperature cooking and processing. Here we review publicly-available genome data for asparagine synthetase genes from species of the Pooideae subfamily, including bread wheat and related wheat species (Triticum and Aegilops spp.), barley (Hordeum vulgare) and rye (Secale cereale) of the Triticeae tribe. Also from the Pooideae subfamily: brachypodium (Brachypodium dystachion) of the Brachypodiae tribe. More diverse species are also included, comprising sorghum (Sorghum bicolor) and maize (Zea mays) of the Panicoideae subfamily, and rice (Oryza sativa) of the Ehrhartoideae subfamily. The asparagine synthetase gene families of the Triticeae species each comprise five genes per genome, with the genes assigned to four groups: 1, 2, 3 (subdivided into 3.1 and 3.2) and 4. Each species has a single gene per genome in each group, except that some bread wheat varieties (genomes AABBDD) and emmer wheat (Triticum dicoccoides; genomes AABB) lack a group 2 gene in the B genome. This raises questions about the ancestry of cultivated pasta wheat and the B genome donor of bread wheat, suggesting that the hybridisation event that gave rise to hexaploid bread wheat occurred more than once. In phylogenetic analyses, genes from the other species cluster with the Triticeae genes, but brachypodium, sorghum and maize lack a group 2 gene, while rice has only two genes, one group 3 and one group 4. This means that TaASN2, the most highly expressed asparagine synthetase gene in wheat grain, has no equivalent in maize, rice, sorghum or brachypodium. An evolutionary pathway is proposed in which a series of gene duplications gave rise to the five genes found in modern Triticeae species.

KeywordsGene family evolution; Asparagine metabolism; Asparagine synthetase; Amino acids; Acrylamide; Food safety; Wheat; Barley; Rye; Rice; Brachypodium; Maize; Sorghum; Wheat evolution
Year of Publication2020
JournalAnnals of Applied Biology - AAB
Digital Object Identifier (DOI)https://doi.org/10.1111/aab.12632
Web address (URL)https://onlinelibrary.wiley.com/doi/abs/10.1111/aab.12632?campaign=wolacceptedarticle
Open accessPublished as ‘gold’ (paid) open access
FunderBiotechnology and Biological Sciences Research Council
Funder project or codeSWBio DTP PhD studentship
Designing Future Wheat (DFW) [ISPG]
Output statusPublished
Publication dates
Online01 Aug 2020
Publication process dates
Accepted14 Jul 2020

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