A new joint study by the University and the University of California (Davis) successfully identified a cluster of genes (OPR III) responsible for regulating the length of roots in bread wheat. The discovery will make it possible develop wheat cultivars with longer roots in order to reach deeper layers of the soil and to absorb more water and nutrients, which can significantly improve yields in arid conditions and low precipitation. “This is the first time that a gene associated with drought tolerance has been discovered and its function is validated in wheat. Given the importance of wheat for global nutrition, on the one hand, and the fact that global warming is leading to an expansion of arid areas and impairing agricultural crops, on the other, this discovery is highly significant and will allow wheat to be grown in a wider range of climatic conditions,” noted Dr. Gilad Gabay, the first author of an article published in the prestigious journal Nature Communications.
Wheat is one of the three main grains that form the foundation of global nutrition, alongside rice and corn. Global wheat consumption now totals over 800 million tons a year, accounting for 20 percent of total global calory and protein consumption. The vast majority (95 percent) of the wheat used for human consumption belongs to a single species, bread wheat (Triticum aestivum); almost all the remaining five percent is durum wheat (Triticum durum). Experts forecast that by 2050 the demand for wheat will double. At present, however, it is not only impossible to expands the areas where wheat is grown, but due to global warming and climate change existing production areas are becoming too arid to grow wheat, which is a crop that relies on rainfall irrigation. Accordingly, if new ways are not found to increase the pace of wheat production, it is feared that a severe shortage of the crop may develop, potentially sparking a global nutritional crisis. One possible solution to the need to increase wheat crops is genetic improvement in order to increase wheat yields without increasing the production area. About five years ago, the full genome of bread wheat was sequenced thanks to a broad-based international effort, including Prof. Zion Fahima and Prof. Assaf Distelfeld from the Institute of Evolution and Faculty of Natural Sciences at the University. The gene sequencing paved the way to identify the specific genes in bread wheat responsible for various growth processes.
In the current study, Dr. Gabay and Prof. Jorge Dubcovsky of UC Davis, together with Prof. Fahima and research student Hanchao Wang of the University additional researchers from various universities around the world, were able to identify a cluster of genes responsible for regulating the length of wheat roots.
In the first stage of the study, the researchers identified wheat cultivars s in which significant difference were found in the field in yield production (over 2,000 kg per hectare) and in the plant biomass. However, what caught their attention was the fact that these differences were larger in arid conditions. In the second stage, tests in wheat fields and by using hydroponic methods found that these gaps in yield were due to differences in the root lengths. In the third stage, the researchers used advanced genomics and bioinformatics tools to identify the genomic region that may include genes associated with the root architecture in wheat plants. “This identification is considered extremely complex, since bread wheat has an enormous genome – over five times the human genome – that includes three distinct sub-genomes that include six copies of very chromosome,” explains Dr. Gabay. In the final stage, the researchers managed to validate the function of the genes in the development of roots through the use of pioneering genome editing and genetic engineering techniques in wheat research developed recently at the laboratory of Dr. Jorge Dubcovsky. These techniques were implemented by a team including doctoral student Hanchao Wang, under the guidance of Dr. Gilad Gabay, who developed innovative Next Generation Sequencing (NGS) tools to locate mutations in the wheat genome caused by genome editing.
As noted, in the current study the researchers managed to identify the OPR-III gene cluster. They found that the level of gene expression, which was changed by genome editing and molecular tools, or the different copy number of the gene in the various wheat cultivars, influence root length. The researchers also profiled the mechanism through which the genes influence the lengthening of the roots and identified the plant hormone that plays a role in determining root growth rate.
Current regulation in most Western countries does not permit genetic enhancement through artificial intervention designed to change the gene expression; as an alternative, the gene may be transmitted through natural crosses with existing cultivars . This is where the wild cereal gene bank comes into play. One of the largest such banks in the world is found at the University of and directed by Dr. Tamar Krugman, a partner in a follow-on study being undertaken in Haifa. “Our gene bank includes thousands of strains of wild wheat from Israel and around the world. Now that the cluster of genes responsible for root length has been discovered, we can start to look for wild wheat lines that have an optimal level of expression of the OPR-III genes and introgress these onto bread wheat cultivars. This will allow us to develop new bread wheat cultivars with longer roots that are capable of producing higher yield in arid conditions,” Prof. Fahima explains.
The research is supported by the foundations:
BARD US-Israel Agricultural Research and Development Fund, U.S. Department of Agriculture,
Howard Hughes Medical Institute
National Natural Science Foundation of China