A new finding, reported in a global study involving more than a decade of research, could lead to breeding corn crops that can withstand drought and low-nitrogen soil conditions and ultimately alleviate global food insecurity, according to Penn State leadership. A team of international researchers.
In results published March 16 in the Proceedings of the National Academy of Sciencesthe researchers identified a gene that encodes a transcription factor–a protein useful in converting DNA into RNA–that triggers a genetic sequence responsible for the development of an important trait that enables maize roots to obtain more water and nutrients.
This observable trait, or phenotype, is called scale aerial roots and leads to the formation of air passages in the roots, according to research team leader Jonathan Lynch, Distinguished Professor of Botany. His team at Penn State showed that this phenotype makes roots metabolically cheaper, enabling them to better explore the soil and pick up more water and nutrients from dry, infertile soil.
Now, identifying the genetic mechanism behind the trait creates a target for reproduction, noted Lynch, whose research group in the College of Agricultural Sciences has been studying root traits in maize and beans in the United States, Asia, Latin America, Europe and Africa for more information. from three decades with the aim of improving crop performance.
This latest research was led by Hannah Schneider, formerly a PhD student and then a postdoctoral researcher in Lynch’s lab, and now an assistant professor of crop physiology at Wageningen University and Research in the Netherlands. In the study, it used powerful genetic tools developed in previous research at Penn State to achieve “high-throughput phenotypes” by measuring the characteristics of thousands of roots in a short time.
Using techniques such as laser ablation tomography and an anatomy pipeline, along with genome-wide association studies, she found that the gene – ‘bHLH121 transcription factor’ – that causes maize to express cortical aerial roots. Schneider noted that locating and then validating the genetic bases of root traits required a lengthy effort.
“We first conducted the field trials that went into this study starting in 2010, planting more than 500 strains of corn at sites in Pennsylvania, Arizona, Wisconsin, and South Africa,” she said. “I worked at all of those sites. We saw compelling evidence that we’d located a gene associated with the cortical rhizosphere.”
But Schneider said the proof of concept took a long time. The researchers created multiple mutant maize lines using gene manipulation methods such as the CRISPR/Cas9 gene editing system and gene knock-downs to show the causal relationship between the transcription factor and the formation of cortical aerial roots..
““It took years not only to create these lines, but also to phenotype them in different conditions to validate the function of this gene. We spent 10 years on this, to confirm and validate our results, to make sure that this is true,” she said. Gene and specific transcription factor that controls the formation of aerial cortical roots. Doing this kind of work in the field and extracting and placing the roots of mature plants was a long process. “
In the paper, the authors report that functional studies revealed that a maize line mutant with the bHLH121 gene was interrupted and a CRISPR/Cas9 mutant line in which the gene was edited to suppress its function both showed reduced cortical root formation. By contrast, the overexpressing line showed significantly greater formation of the air cortex root when compared to the wild-type maize line.
Characterization of these lines under suboptimal water and nitrogen availability in multiple soil environments revealed that the bHLH121 gene is required for aerial cortical root formation, according to the researchers. They suggested that comprehensive validation of the importance of the bHLH121 gene in cortical root formation provides a new marker for plant breeders to select cultivars with improved soil exploration, and thus yield, under suboptimal conditions.
For Lynch, who plans to retire from the College of Plant Sciences at the end of this year, the research is the culmination of 30 years of work at Penn State.
“These results are the result of many people in Pennsylvania and beyond collaborating with us and working over many years,” he said. “We discovered the function of the aerenchyma trait and then the gene associated with it, and that arose because of technologies that were being pioneered here at Penn State, such as Shovelomics — field root drilling — laser tomography and Pipeline Anatomics. We put all of those together in this work.”
The findings are significant, Lynch said, because finding a gene behind an important trait that will help plants better tolerate drought and better pick up nitrogen and phosphorus looms large in the face of climate change.
“These are very important qualities – both here in the United States and around the world,” he said. “Drought is the biggest risk to corn growers and gets worse with climate change, and nitrogen is the biggest cost to growing corn, from both a financial and environmental perspective. Breeding corn lines more efficiently foraging for nutrients would be a huge development.”
Contributing research was Penn State’s Kathleen Brown, Professor of Plant Stress Biology, now retired; Meredith Hanlon, Postdoctoral Researcher, Department of Plant Science; Stephanie Klein is a doctoral student in plant sciences. and Cody Debo, Postdoctoral Researcher, Department of Plant Sciences; Faye Lorre, Sean Keppler, and Xia Zhang, Department of Agronomy and Wisconsin Crop Innovation Center, University of Wisconsin; Patompong Saengwilai, Department of Biology, College of Science, Mahidol University, Bangkok, Thailand; Jane Davis, Rahul Bussell and Malcolm Bennett, Beacon of the Future Food and School of Biological Sciences, University of Nottingham, Loughborough, UK; Aditi Purkar, Faculty of Veterinary Medicine and Science, University of Nottingham, Sutton Bonington, UK.
The US Department of Energy, the Howard G. Buffett Foundation, and the US Department of Agriculture’s National Institute of Food and Agriculture supported this research.
