The discovery of a gene called called ZmCIPK15 that regulates the angle of root growth in corn can serve as a new tool to enable the breeding of deeper-rooting crops with enhanced ability to take up nitrogen, according to an international team of researchers, led by Penn State.
IDENTIFICATION OF THE GENE
The gene, called ZmCIPK15, a moniker indicating where it is located in the genome and how it functions, was found to be missing in a naturally occurring mutant corn line that grows roots at steeper angles that make them go deeper into the soil. The gene was identified using the technique called a genome-wide association study, which involves a painstaking statistical analysis of a genome-wide set of genetic variants in different plant lines to see what genes are associated with a trait.
Researchers at Penn State screened nearly 500 lines of corn over four years in South Africa, to find the gene regulating the angle of roots . Field experiments at Penn State’s Russell E. Larson Agricultural Research Center and greenhouse experiments at the University Park campus were conducted to confirm the phenotype of the mutant and wild-type plants and to test the functional utility of changes in root angle for nitrogen capture. Roots of selected plants were excavated and measured, validating the functional importance of the ZmCIPK15 gene. It caused an approximate 10-degree change in root angle, noted Hannah Schneider, a former postdoctoral scholar in the Lynch lab, now a faculty member at Wageningen University in the Netherlands, who spearheaded the research.
The gene that controls the angle of root growth in corn — influencing the depth to which roots forage — is important because deeper roots have a greater ability to capture nitrogen, according to research team leader Jonathan Lynch, distinguished professor of plant science in Penn State’s College of Agricultural Sciences. Such corn with an enhanced ability to take up nitrogen has implications for the world’s environment, economy and food security is duly noted.
The above images of root architecture in the field showing the cipk15 mutant corn genotype had significantly steeper angles compared to the wildtype genotype. Plants were grown in low nitrogen conditions. The mutant corn line that produced the root on the right lacks a gene that regulates root growth.
NEW FINDINGS OF THE STUDY
- In findings ,recently published in Plant, Cell and Environment, the researchers reported that a steeper root growth angle markedly improved nitrogen capture which meant enhanced deep nitrogen acquisition
- It was also expected to see that the steeper growth angle of cipk15 mutants’ roots would result in better performance in drought, but in experiments carried out by them, it did not translate to improved plant water status which maybe because of the difficulty in simulating drought conditions in Pennsylvania as predicted by the researchers.
- When a single gene was knocked out, the crop showed deeper roots and better nitrogen capture. This was quite unusual as by knocking something out, that the plant gets better. Plants are like finely tuned machines; it’s not expected to work better when a gene is taken out of finely tuned machine as stated by Lynch.
- Infield studies under suboptimal nitrogen availability, the cipk15 mutant with steeper growth angles had 18 per cent greater shoot biomass and 29 per cent greater shoot nitrogen accumulation compared to the wild type, after 70 days of growth
Corn is one of the most important crops in the world. In countries like the U.S., the biggest energy, economic and environmental cost of growing corn is nitrogen fertilizer and more than half of which, that is applied to corn is not even taken up. It’s wasted and washed deeper into the soil polluting groundwater, and some of it also goes into the atmosphere as the greenhouse gas, nitrous oxide causing a massive problem as said by Lynch
In contrast, in regions like Africa where people are very much dependent on corn for food, soils are nitrogen deficient in field and farmers can’t afford to buy fertilizer if it even is available, Lynch added. Corn yields in Africa are just a fraction of what they are in the U.S.
Deeper-rooting corn would help poor countries like Africa harvest more food with the limited amount of nitrogen that they have.
“For America, here’s a way to reduce a major cost and environmental impact from corn production. For Africa, this discovery could result in higher corn yields that will reduce food insecurity. And this discovery may support the discovery of genes regulating steeper root angles for other cereal plants, especially those closely related to corn, like sorghum and pearl millet.” stated Jonathan Lynch, distinguished professor of plant science in Penn State’s College of Agricultural Sciences.