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Bread Wheat Genome Sequenced

Growing wheat

(walfred, Pixabay)

17 August 2018. An international collaboration published a complete, annotated genomic sequencing of wheat used in making bread, a widely grown staple crop and major source of nutrition worldwide. A report of the bread wheat sequence, a project of the International Wheat Genome Sequencing Consortium in Bethesda, Maryland, appears in today’s issue of the journal Science (paid subscription required).

Wheat grown for food is the most widely cultivated crop, accounting for about one-fifth of all calories and protein consumed, and feeding more than one-third of the world’s population. As the demand for food overall and bread in particular is rising, say the authors, wheat growers are facing increasing challenges to their yields from natural obstacles such as pests, as well as heat and drought from a changing climate. Despite this large and growing demand, an understanding of wheat’s genome — the foundation for modifying the plant’s traits to meet these challenges — remained incomplete, due largely to the plant’s complexity.

Wheat’s genome is both large and complex, more than 5 times the size of the human genome. The plant’s genome is also a combination of 3 ancestral varieties, with 85 percent of the genes repeating, adding to the difficulty of deconstructing the genome. In the end, it took some 200 researchers from 20 countries — representing academic labs, growers, and seed companies — to develop the reference genome described in the Science paper. The team analyzed the genome of the bread wheat variety known as Chinese spring or common wheat, Triticum aestivum L.

Their analysis reveals 21 chromosomes containing nearly 108,000 genes. The sequencing also identifies some 4 million genetic variations and fragments, as well as the relationships between these molecular markers and genes that influence the regulation of the genes’ expression. From this assembly of genes and associated markers, the researchers were able to identify gene expression networks in wheat for all stages of the plant’s development.

The sequencing data, published as a reference document and made freely available through the consortium, are expected to help growers and seed companies improve the ability of bread wheat to withstand climatic challenges and pests, as well as create varieties that do not cause adverse allergic reactions, such as in celiac disease. Genome editing techniques such as Crispr, for example, could remove genes responsible for proteins like gluten that cause allergic reactions, while retaining elements needed for wheat plants to grow and survive.

A second article in the same issue of Science offers an immediate use of the sequencing data. Another international team, including researchers who sequenced the genome, analyzed the data to identify gene copies throughout the genome that originate in the 3 separate ancestral forms that make up today’s bread wheat plants. The researchers focused specifically on gene expression patterns of plant tissue related to stress, comparing 850 RNA transcriptions from the genes with the reference genome to identify similarities and differences in the gene copies. The results are expected to help design new varieties able to better resist those stresses.

Researchers taking part in the project and officials with the International Wheat Genome Sequencing Consortium tell more about the project in the following video.

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