Breakthrough in plant disease: New enzyme could lead to anti-bacterial pesticides
Researchers uncover the crucial role of OpgD enzyme in enhancing Xanthomonas pathogenicity
image:
Scientists identified the cyclic compound as CβG16α.
view moreCredit: Masahiro Nakajima from Tokyo University of Science
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. Therefore, accurately identifying the pathogens responsible for these diseases is crucial. This identification allows for targeted interventions that minimize risks and effectively mitigate the agricultural impacts.
Xanthomonas species are notorious plant pathogens that affect a broad spectrum of hosts, including key crops like rice, wheat, and tomatoes. These pathogens augment their pathogenicity by utilizing α-1,6-cyclized β-1,2-glucohexadecaose (CβG16α) to suppress essential plant defense mechanisms, such as the expression of pathogenesis-related proteins and the accumulation of callose.
In a recent breakthrough published on June 19, 2024, in the Journal of the American Chemical Society, a team of researchers led by Associate Professor Masahiro Nakajima from Tokyo University of Science unveiled a significant discovery. They identified XccOpgD, a glycoside hydrolase (GH186) found in X. campestris pv campestris which plays a pivotal role in the biosynthesis of CβG16α. The research team also included Mr. Sei Motouchi from Tokyo University of Science, Principal Scientist Shiro Komba from the Institute of Food Research, NARO, and Hiroyuki Nakai from Niigata University.
“Glycan structures are intricate and multifaceted and fulfill 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,” explains Prof. Nakajima, elaborating on the study's rationale.
The team conducted biochemical analysis to elucidate the role of XccOpgD in CβG16α biosynthesis. Advanced techniques such as X-ray crystallography were employed as structural analysis to unravel the enzyme's catalytic mechanism and substrate specificity.
These efforts have yielded profound insights. XccOpgD belongs to the GH186 family, essential for regulating bacterial cell wall components. Unlike the first identified GH186 enzymes, XccOpgD exhibits an unprecedented enzymatic mechanism known as anomer-inverting transglycosylation.
“Reactions of typical GH enzymes are classified into four types by combination of retaining or inverting, and reaction with water (hydrolysis) or sugar (transglycosylation) theoretically. However, one classification is missing somehow in a long history of researches on carbohydrate associated enzymes and we discovered the missing classification. This breakthrough was made possible by unique structural environment, opening new possibilities for enzyme-based glycosylation,” explains Prof. Nakajima. Moreover, the sugar chains synthesized through this mechanism are not merely minor components but rather essential structures utilized by various Gram-negative bacteria in nature for pathogenic purposes.
Detailed studies revealed that linear β-1,2-glucan was converted to cyclic compound and the compound was identified as CβG16α using nuclear magnetic resonance. Structural analysis of the Michaelis complex identified crucial substrate binding residues, further elucidating specific interactions along the glucan chain. Notably, XccOpgD utilizes an anomer-inverting transglycosylation mechanism, with D379 and D291 playing pivotal roles as catalysts.
These findings deepen our understanding and open avenues for developing targeted strategies against Xanthomonas-induced plant diseases. “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,” says a hopeful Prof. Nakajima.
The discovery of XccOpgD and its role in CβG16α biosynthesis marks a major breakthrough in agriculture. It promises enhanced resilience and food security while mitigating environmental impacts linked to conventional pesticides. Overall, this advancement offers sustainable solutions to global agricultural challenges, promoting environmental stewardship and economic viability for farmers worldwide.
Unveiling XccOpgD: Key Player in Plant Pathogen Defense
Scientists uncover XccOpgD's role in enhancing Xanthomonas pathogenicity.
Credit
Masahiro Nakajima from Tokyo University of Science
***
Reference
DOI: 10.1021/jacs.4c02579
Authors: Sei Motouchi1, Shiro Komba2, Hiroyuki Nakai3, and Masahiro Nakajima1
Affiliations:
1Department of Applied Biological Science, Tokyo University of Science
2Institute of Food Research, National Agriculture and Food Research Organization
3Faculty of Agriculture, Niigata University
Funding information
This work was supported in part by JST SPRING (Grant 386 Number JPMJSP2151).
Journal
Journal of the American Chemical Society
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Discovery of Anomer-Inverting Transglycosylase: Cyclic Glucohexadecaose-Producing Enzyme from Xanthomonas, a Phytopathogen
New research sheds light on relationships between plants and insects in forest ecosystems
image:
Seana Walsh from the National Botanical Garden in Kauaʻi collects leaf litter at Kokeʻe State Park in Kauaʻi.
view moreCredit: Photo by Nina Ronsted
U.S. Forest Service researchers and partners published new findings on how leaf-eating insects affect forest ecosystems worldwide.
“The findings of this study provide an improved understanding of the intricate relationship between herbivorous insects and forest ecosystems,” Bernice Hwang, the paper’s lead author and former U.S. Forest Service technician, stated.
Hwang and fellow researchers are aware of how large herbivores cycle nutrients in forests. They know much less, however, about how leaf-eating insects impact forest carbon and nutrient cycling. And they were determined to find out.
Their first step was establishing a global network of 74 plots within 40 mature, undisturbed broadleaved forests. They analyzed leaf litter and green leaves for carbon, nitrogen, phosphorus and silica concentrations. Leaf production, how much insects feed on leaves, and fluxes in nutrient levels from other sources also informed their research.
Chistian Giardina and Nels Johnson of the Pacific Southwest Research Station and other researchers found that insects play a significant role in releasing and cycling vital nutrients in forest ecosystems. This was particularly true for warmer climates like those in tropical forests.
Their findings suggest that a warming climate can affect how plants and herbivores interact. Changes in those relationships have important consequences for carbon and nutrient cycling in broadleaved forests on a global scale.
The researchers hope this new knowledge can contribute to a better understanding of forest ecosystems and inform efforts to conserve them.
“I believe this analysis will be a benchmark to compare against for its field,” Johnson noted.
Journal
Nature Communications
Method of Research
Data/statistical analysis
Subject of Research
Not applicable
Article Title
The impact of insect herbivory on biogeochemical cycling in broadleaved forests varies with temperature
No comments:
Post a Comment