The overarching goal of this project is to understand the mechanisms by which bacteria cause disease to plants. This project focuses on one group of bacteria, called Rhodococcus. Most bacteria are not pathogenic to plants and are associated with beneficial effects, such as promoting growth of plants and protecting them from disease caused by other pathogens. However, Rhodococcus can acquire extra DNA called plasmids that transition them to being pathogenic. Hence, genes on these plasmids are critical for these bacteria to cause disease, which is typically associated with disfigured growth. This disease results in millions of dollars of damage to US agriculture. By understanding how plasmid-borne genes function and manipulate the genome of the bacteria to cause disease, this project will inform on strategies to help US growers mitigate disease risks. As part of the project, there will be two outreach components designed to address goals of increasing participation by underrepresented students. Summer biology camps will be delivered to high school students to learn the scientific process and give them a college experience. Long-term, mentored research opportunities will be provided to undergraduate students to help prepare them for careers in the sciences.
Virulence plasmids are necessary and sufficient to transition Rhodococcus to being a pathogen of plants. Two plasmid loci have been identified as necessary. The fasR locus encodes a transcription factor. The fas locus encodes proteins implicated in the metabolism of cytokinins. The regulon of fasR remains unknown. In contrast, a long-standing hypothesis suggests that cytokinins, which are best known as plant growth promoting hormones, are synthesized by microbes to directly manipulate plant hosts. Research will test an alternative hypothesis that plasmid-encoded genes and cytokinins coopt and reprogram chromosomal genes for virulence. Three aims are designed to determine the necessity and sufficiency of genes in pathogenesis, understand how virulence genes are regulated, and test the role of cytokinins in regulating virulence of bacterial pathogens. To accomplish these aims, the project will use molecular genetic approaches and whole transcriptomics as well as proteomics studies to uncover how plasmid borne virulence genes alter the expression patterns of chromosomal genes to cause disease to plants.
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.
