Elucidation of serine hydroxymethyltransferase-mediated mechanisms of nematode disease resistance

The soybean cyst nematode (SCN), a microscopic soil-borne roundworm, is a widespread pathogen of soybean and a billion dollar problem in US agriculture. Decades of planting a single type of genetic resistance has led to widespread virulence of this pathogen on commercially available SCN-resistant soybean cultivars reducing their overall effectiveness.

The goal of this project is to better understand the resistance mechanisms of the soybean plant to gain insight into how SCN are able to adapt to overcome it and enable the design of more durable resistance in soybean. The investigators will study the genetic differences found in a type of soybean linked with increased resistance to SCN, but currently not broadly available to soybean producers.

These genetic changes affect a soybean enzyme involved in folate metabolism known as serine hydroxymethyltransferase 8 (SHMT8). Using a combination of scientific approaches, including structural biology and plant-based studies, the impacts of the genetic differences in SHMT8 on the soybean plant will be characterized and used to develop new ways to fight SCN infestations in soybean fields.

This is a collaborative effort between two investigators with complementary expertise: the structural biology and biochemical studies will be performed at the University of Missouri and the plant-based studies will be conducted at the University of Georgia. Graduate and undergraduate researchers involved in the project will participate in a 2-week experiential learning summer exchange program between the PIs’ laboratories at the Universities of Missouri and of Georgia, to gain exposure to the complementary disciplines in both laboratories.

Undergraduates, including women and underrepresented minorities, will directly participate in the research efforts. A week-long Nematode Boot Camp each summer targeting K-5 underrepresented minorities will engage graduate and undergraduate students in science outreach for improved STEM education.

The soybean cyst nematode (SCN), a microscopic roundworm, is the most important pathogen of soybean. Current management relies almost exclusively on the use of SCN resistant soybean cultivars. Unfortunately, this approach has become less effective over time as nematodes have adapted to the commercially available resistant soybean genotypes.

This project aims to provide a molecular understanding of the basis of SCN resistance in soybeans and thereby enable the development of more durable resistance and potentially novel strategies for combating this destructive agricultural pathogen. Specifically, this project will focus on studies of the soybean enzyme serine hydroxymethyltransferase 8 (SHMT8), which has genetic differences linked to SCN resistance: the “resistant version” of SHMT8 differs by only two amino acids relative to SHMT8 found in SCN susceptible soybean cultivars.

Structural, biochemical and biophysical characterization of SHMT8 is proposed to help unravel how the molecular differences in SHMT8 translate to SCN resistance in soybean. This work will be complemented by plant-based studies to elucidate SHMT8-mediated metabolic perturbations in soybean roots in response to SCN infection and host pathways that affect soybean resistance.

Plant-based studies employing modern genome editing tools will also be critical for confirming novel hypotheses regarding SCN resistance derived from the in vitro studies. In addition to benefits for soybean agriculture, a critical part of the U.S. economy, this collaborative research project spans the areas of X-ray crystallography, protein chemistry, plant-pathogen interactions, and soybean molecular genetics.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.