Under the wide prairie skies of Saskatoon, discoveries are being made about wheat that may have broad and far-reaching implications across the biological sciences. Researchers started out by seeking practical solutions to a common problem – the need to address climate change impacts and increase yield under dry conditions in wheat and other cereal crops.
This important work is being done by a team of researchers at the National Research Council of Canada's (NRC) Aquatic and Crop Resource Development Research Centre. As Dr. Allan Feurtado points out, "there isn't a year that goes by on the Prairies where crops aren't under a degree of water stress." Project colleagues Dr. Daiqing Huang and Dr. Adrian Cutler agree, and also point to the global nature of the challenge. With 60% of the world's food energy intake derived from cereal crops, it's an urgent issue.
A protective coating for wheat
In 2013, the team began exploring waxes that provide a natural protective coating, a most important feature that reduces water loss, making crops more resistant to drought. Specifically, diketone waxes are a special type of wax only found in wheat and a few other cereals. The team partnered with Agriculture and Agri-Food Canada to obtain a set of specially designed wheat lines that had been developed in the 1990s.
The team's approach was to compare wax composition, gene expression (messenger ribonucleic acid (mRNA) transcribed from genes) and small regulatory RNAs (microRNAs) between the pairs of lines. They identified four genes in two categories that controlled the production of the special diketone waxes: three genes coded for proteins involved in diketone wax biosynthesis and one gene that inhibited wax production but did not code for a protein
After months of experiments and analysis, they identified a non-protein coding gene from which a microRNA is produced that represses one of the biosynthetic genes. When the inhibitor gene is expressed, no diketone waxes are produced. By comparing gene sequences, the team deduced that the inhibitor gene evolved from the biosynthetic gene that it targets. Their discovery of the wax inhibitor gene – a non-coding RNA gene – was a first.
"That discovery lays the foundation for new and important research. You have to understand which genes are involved in a particular process before you can discover how to optimize the trait," Feurtado explained. The team now had both pieces of the puzzle – the genes that produce wax and the gene that inhibits wax production. With that knowledge in hand, researchers can work towards modulating wax content for particular environments.
Looking ahead, the team sees this discovery as one element in the search for better crop stability and yields. Adrian Cutler shared his vision: "In the future, plant breeders will need information on the hundreds – and perhaps thousands – of genes that contribute to yield and protein content in grains. This research is a contribution to an emerging inventory of all the genes that will go into making high-performance wheat for the future.
Daiqing Huang added, "The wax layer provides a protective surface on the plant that is important in fighting abiotic stress like drought, ultraviolet (UV) radiation and high temperatures, as well as biotic stress from insects and disease." Plants able to withstand these stresses offer producers better yield stability in less than perfect crop conditions. "It may improve wheat yield stability worldwide where, in the long term, more drought-tolerant varieties are needed for food security."
Cutting-edge science – from wheat to other breakthroughs
The significance of the discovery lies in the unique regulatory function of the wax inhibitor gene. "There are more of these non-coding RNA genes than anyone had previously realized 10 or even 5 years ago. And it may offer new directions for biological science," commented Cutler.
Collaborating for success
Huang, Cutler and Feurtado credit the collaborative foundation of the project. "It wasn't easy to find and validate the wax inhibitor microRNA sequence - 21 base pairs long – in the gigantic 17 gigabase wheat genome. It required comprehensive knowledge of genomics, genetics, bioinformatics and molecular biology, and to take a creative approach to solving problems," said Huang. Colleagues in the NRC's plant growth, plant sequencing, and plant transformation facilities, as well as the bioinformatics team, were instrumental in their success.
Looking ahead, they are focused on their discovery's potential. "Our ultimate goal," said Feurtado, "is to help make wheat more productive for Canadian farmers."