After 13 long years, scientists have achieved the once ‘impossible’ task of mapping the genome of wheat. Wheat is the most widely grown crop worldwide and is essential for food security, therefore, decoding its complex genome has unsurprisingly been an important goal. In the paper published on August 17 in Science, the wheat genome was presented by the International Wheat Genome Sequencing Consortium in all its glory. The international team of researchers focused on a common wheat cultivar called Chinese Spring.
Why has it taken this long to map the genome of one of the most important agricultural crops on the planet? The simple reason is that the genome of wheat is both huge and highly complex. In fact, wheat does not have just one genome but three overlapping sub-genomes, stretching to more than five times the length of the human genome. Moreover, the wheat genome has somewhere in the region of 107, 000 genes compared to the seemingly meek 24,000 genes of humans, and to add to this chaos, 85% of the genome is composed of repeated elements.
Why is this breakthrough so important? For starters, decoding the genome of many species of plants and animals has coincided with the development of gene editing technologies, such as CRISPR-Cas9. Tools like these will enable the precise manipulation of genomes thus enabling the production of wheat varieties with higher yields, enhanced nutritional quality, and improved sustainability, as well as more robust pest-resistant varieties of wheat. Furthermore, unravelling the sequences of wheat genes may contribute to a better understanding of bread allergies and immune diseases, and lead to potential treatments or solutions.
This may be good news for those who suffer from wheat and gluten-related issues, including allergies like baker’s asthma and both coeliac disease and non-coeliac wheat sensitivity, which are now known to be caused by various unrelated mechanisms. An associated paper, led by Angela Juhász of Murdoch University in Western Australia, also published on August 17 in Science Advances, found that coeliac disease ― characterised by an immune reaction in response to eating gluten ― is related to the glutenins and gliadins expressed in the starchy endosperm of the wheat grain, which is what makes it difficult to break down the large proteins found in gluten. Whereas Baker’s asthma is triggered by another set of allergens, including amylase trypsin inhibitors, found in a thin layer of cells that surround the endosperm.
Now that a high-quality reference sequence of the bread wheat genome exists, other possibilities include editing the genome so that it contains more digestible proteins or identifying particular varieties of wheat that contain easier-to-digest gluten. Most importantly, this new information could be used to secure wheat production in order to meet future global demands. This could be achieved by creating hardier wheat varieties with better grain quality that are resistant to fungal diseases and more tolerant of the increasing environmental stresses owing to worsening climate change, thereby improving yields.
(1) The International Wheat Genome Sequencing Consortium (IWGSC). Shifting the limits in wheat research and breeding using a fully annotated reference genome. Science (2018). DOI: 10.1126/science.aar7191
(2) Juhász, A. et al. Genome mapping of seed-borne allergens and immunoresponsive proteins in wheat. Science Advances (2018). DOI: 10.1126/sciadv.aar8602