Cultivated oat (Avena sativa) is an allohexaploid crop thought to have been domesticated more than 3,000 years ago while growing as a weed in wheat, emmer and barley fields in Anatolia. Oat has a low carbon footprint, substantial health benefits and the potential to replace animal-based food products. However, the lack of a fully annotated reference genome has hampered efforts to deconvolute its complex evolutionary history and functional gene dynamics.
Oat (Avena sativa). Image credit: Hans Braxmeier.
Oat belongs to Poaceae, an economically important grass family that includes wheat, rice, barley, common millet, maize, sorghum and sugarcane.
All species in its genus, Avena, exist in nature as diploids, tetraploids and hexaploids and exhibit the greatest genetic diversity around the Mediterranean, Middle East, Canary Islands and Himalayas.
Currently, oat is a global crop with production ranking seventh among cereals.
Compared with that of other cereals, its cultivation requires fewer treatments with insecticides, fungicides or fertilizers.
Whole-grain oats are a healthy source of antioxidants, polyunsaturated fatty acids, proteins and dietary fiber such as beta-glucan, which is important in post-meal glycemic responses and for preventing cardiovascular disease.
Cereals such as wheat, barley and rye store high amounts of gluten proteins in their grain; by contrast, oat and rice store globular proteins in their grain.
“Oat milk is a very high-quality product that tastes good and serves as a vegan milk substitute,” said Dr. Martin Mascher, a researcher at the IPK Leibniz Institute.
“Unlike wheat and barley, oat is used directly as food. Barley is used for brewing, wheat for baking bread, but oat, for example in the form of oatmeal, is still very close to the original grain.”
The oat genome is composed three subgenomes that were donated by three wild species of Avena in the past 10 million years.
“Avena species have six sets of chromosomes with more than 80,000 genes in total, while humans have only two sets of chromosomes with about 20,000 genes,” the scientists said.
“Moreover, the order of genes along the chromosomes is substantially less sorted than in other cereals with a considerable amount of genes having been relocated between the chromosomes, resulting in a mosaic-like genome architecture.”
In the research, they produced a chromosome-scale reference sequence of the oat cultivar Sang.
They also assembled pseudochromosomes of diploid Avena longiglumis and tetraploid Avena insularis.
“Knowing a genome sequence allows us to better understand which genes are responsible for which traits,” the authors said.
“In the case of oats, we were particularly interested in finding out why they trigger fewer allergies and intolerances compared to cereals such as wheat or rye.”
“We discovered that oats have fewer of the proteins that correspond to gluten in wheat. Since these proteins are directly related to celiac disease and wheat intolerances, oats lead to fewer intolerances in humans.”
“This allowed us to confirm on a genomic level that oats in their pure form are suitable for a gluten-free diet.”
“Compared to other cereals, oats also contain a much higher proportion of so-called beta-glucans,” they added.
“These dietary fibers reduce cholesterol in the blood and have a positive influence on people with metabolic diseases such as type 2 diabetes.”
“Thanks to the sequencing effort, we now know which genes are responsible for the health-promoting beta-glucans.”
Thanks to the new insights into the oat genome, breeding and cultivation of more nutritious and sustainable oats can now be accelerated.
“We have created the potential for targeted breeding, since we are now able to tell which oat varieties are compatible with another,” said Dr. Nick Sirijovski, a researcher at Lund University and ScanOats.
“At this point, we can combine traits for an even more favorable health profile, higher yields, better resistance to parasites and drought, and most importantly, in preparation for climate change.”
The findings appear in the journal Nature.
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N. Kamal et al. The mosaic oat genome gives insights into a uniquely healthy cereal crop. Nature, published online May 18, 2022; doi: 10.1038/s41586-022-04732-y
Source link: https://www.sci.news/genetics/oat-genome-10820.html
