EAGER: Plant pathogenic Streptomyces encode components for genetic code mistranslation

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This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117- 2). Plant-pathogenic microorganisms are ubiquitous in soils across the U.S. and negatively affect the production of vital food crops and the country’s agricultural economy. Understanding the biological mechanisms to infect and colonize plants employed by these microbes is fundamental for the development of effective management approaches. The present project will investigate novel protein factors that are uniquely encoded by a group of plant-associated microbes, including several pathogens responsible for the common scab disease in potatoes and other tubers. Early research indicates that the protein factors endow these pathogens with the ability to deliberately alter their genomic information without changing their DNA, and ultimately can result in the production of multiple protein mutants from a single gene. Why these pathogens encode these dedicated factors and how they function is largely unknown. The goals of this project are to determine the function of these factors and to explore their role in plant pathogenicity of their host species. Importantly, the implementation of this work will involve the training of two postbaccalaureate associates from underrepresented groups in STEM and will offer opportunities for undergraduate students to gain a first-hand research experience.The genetic code assigns each of the twenty canonical amino acids to one of the 61 sense codons. One of the only two exceptions to the rule of one codon specifying one amino acid was recently discovered in a small group of plant pathogens from the bacterial Streptomyces family, including Streptomyces turgidiscabies and Streptomyces scabiei. These organisms, which are the causative agents of distinct tuber diseases that cause substantial economic losses to U.S. farmers, encode an anomalous aminoacyl-tRNA synthetase and a corresponding tRNA. Expression of these factors causes translation of alanine codons as proline. This dual use of alanine codons enables the diversification and expansion of the host’s proteome due to stochastic Ala→Pro mutations, which can generate a multiplicity of protein variants from a single gene. This may provide a rapid response against stress and environmental changes as well as a mechanism for virulence and infection. This project will combine biochemical, biophysical, multi-omics, comparative genomics, genetics, and molecular biology approaches to elucidate the molecular interactions and features that enabled the emergence of these translation factors and to explore their biological function in the pathogenic Streptomyces hosts.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.