Plant disease breakthrough could lead to anti-bacterial pesticides
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Researchers from Tokyo University of Science have uncovered a pivotal enzyme with a critical role in synthesizing a key compound used by Xanthomonas pathogens to enhance their virulence against plants.
The discovery of XccOpgD and its role in plant disease marks a major breakthrough in agriculture and opens new avenues for developing targeted pesticides that combat plant diseases without harming beneficial organisms.
It promises enhanced resilience and food security while mitigating environmental impacts linked to conventional pesticides.
Plant diseases pose significant challenges to agricultural productivity, presenting formidable hurdles that require urgent attention. Left unchecked, these diseases can spread rapidly, inflicting widespread damage on crops and leading to reduced yields and substantial economic losses.
Accurately identifying the pathogens responsible for these diseases allows for targeted interventions that minimize risks and effectively mitigate the agricultural impacts.
Xanthomonas species affect a broad spectrum of hosts, including key crops like rice, wheat, and tomatoes. They use α-1,6-cyclized β-1,2-glucohexadecaose (CβG16α) to suppress essential plant defence mechanisms, such as the expression of pathogenesis-related proteins and the accumulation of callose.
The research published in the identified XccOpgD, a glycoside hydrolase (GH186) found in X. campestris pv campestris which plays a pivotal role in the biosynthesis of CβG16α.
The team of researchers was led by Associate Professor Masahiro Nakajima from Tokyo University of Science and also included Sei Motouchi from Tokyo University of Science, Principal Scientist Shiro Komba from the Institute of Food Research, NARO, Hiroyuki Nakai from Niigata University.
They conducted biochemical analysis to elucidate the role of XccOpgD in CβG16α biosynthesis, and used advanced techniques such as X-ray crystallography to unravel the catalytic mechanism and substrate specificity of the enzyme.
These efforts have yielded profound insights. As a result, they found that XccOpgD belongs to the GH186 family, essential for regulating bacterial cell wall components. However, unlike other GH186 enzymes, the newly discovered enzyme acts through an unprecedented mechanism known as anomer-inverting transglycosylation.
Elaborating on the study's rationale, Prof. Nakajima explained: “Glycan structures are intricate and multifaceted and fulfil diverse crucial roles in nature and organisms. Enzymes synthesize and degrade glycans, exhibiting diverse structures and functions that correspond to the glycan diversity. However, our understanding of these enzymes is still limited, which drives the search for new enzymes with varied new potentials.
“We are expecting a pesticide concept targeting this enzyme homolog in the future. Unlike fungicides that promote the emergence of drug-resistant bacteria in soil, targeting this enzyme could potentially inhibit pathogenicity without causing sterilization. Enzyme homologs identified in this study may serve as promising structure-based drug targets, offering a potential solution to the issue of drug-resistant bacteria."
