Join the Van Laar lab!
We are looking for up to three MS Biology students to work on a collaborative project with Dr. Lindsey Burbank at the USDA facility in Parlier. These projects will study the pathogenic capabilities of Xylella fastidiosa, the causative agent of Pierce's Disease in grapes. This bacterium is transmitted by the Glassy-winged Sharpshooter and leads to the death of grapevines (and other plants of agricultural importance). Details of these projects are listed below. Part of the research will be done at the USDA facility in Parlier, so you must be willing to spend time traveling to this facility. If you are interested in one of these graduate positions, please email Dr. Van Laar with your CV, unofficial transcripts, and a cover letter indicating how your qualifications and research interests align with the goals of this project. You must meet the minimum requirements for a graduate student at Fresno State and it is preferred that you have some level of undergraduate research experience, but we are willing to train the right candidates.
Toxin-antitoxin systems in Xylella fastidiosa
The bacterial pathogen Xylella fastidiosa (Xf) is the cause of Pierce’s disease of grapevine which continues to be a serious problem for vineyards in California. The lifecycle of this pathogen involves colonization of very specific environmental niches, mainly the xylem vessels of plant hosts and the mouthparts of insect vectors which transmit Xf between plants. Effective colonization of these environments is dependent on complex bacterial “behaviors” such as biofilm formation, dormancy (persister cell formation), and regulation of bacterial growth based on nutrient availability. Many aspects of the bacterial lifecycle are regulated in part by genes known as toxin-antitoxin (TA) systems. TA systems consist of a toxin protein which degrades messenger RNA in the bacterial cell, and an antitoxin protein which inhibits toxin activity. Expression of different TA systems under different environmental conditions can change the gene expression profile of Xf, contributing to its ability to cause persistent infections in the plant host. Gene expression profiles of six different Xf TA system deletion mutants have been created by RNA sequencing. We will use this expression data to determine which TA systems control different aspects of bacterial growth, plant infection, and/or insect transmission of the pathogen. TA system-regulated pathways identified from the gene expression data will be further characterized by phenotypic analysis of the mutant strains under different laboratory conditions and/or in plant infection and insect transmission experiments.
Cold response of Xylella fastidiosa and winter-curing of Pierce’s disease in grapevine
Pierce’s disease (PD) of grapevine, caused by the bacterial pathogen Xylella fastidiosa (Xf), had led to significant crop losses in vineyards throughout California. An interesting observation about PD is that the disease appears to be limited to warmer climates, and that vines subjected to colder temperatures over the winter are “cured” of the disease by the next growing season. Very little is understood about this phenomenon except that it most likely involves many factors, included susceptibility of the pathogen to cold temperatures, and physiological response of different grapevine varieties to cold and to Xf infection. We will investigate the cold response of Xf using existing mutants in bacterial cold shock proteins and gene expression profiles created by RNA sequencing of Xf under cold stress. We also will investigate differences in winter-curing of Xf from different table grape varieties using cold treatment of Xf-inoculated vines and plant immune response assays.
Toxin-antitoxin systems in Xylella fastidiosa
The bacterial pathogen Xylella fastidiosa (Xf) is the cause of Pierce’s disease of grapevine which continues to be a serious problem for vineyards in California. The lifecycle of this pathogen involves colonization of very specific environmental niches, mainly the xylem vessels of plant hosts and the mouthparts of insect vectors which transmit Xf between plants. Effective colonization of these environments is dependent on complex bacterial “behaviors” such as biofilm formation, dormancy (persister cell formation), and regulation of bacterial growth based on nutrient availability. Many aspects of the bacterial lifecycle are regulated in part by genes known as toxin-antitoxin (TA) systems. TA systems consist of a toxin protein which degrades messenger RNA in the bacterial cell, and an antitoxin protein which inhibits toxin activity. Expression of different TA systems under different environmental conditions can change the gene expression profile of Xf, contributing to its ability to cause persistent infections in the plant host. Gene expression profiles of six different Xf TA system deletion mutants have been created by RNA sequencing. We will use this expression data to determine which TA systems control different aspects of bacterial growth, plant infection, and/or insect transmission of the pathogen. TA system-regulated pathways identified from the gene expression data will be further characterized by phenotypic analysis of the mutant strains under different laboratory conditions and/or in plant infection and insect transmission experiments.
Cold response of Xylella fastidiosa and winter-curing of Pierce’s disease in grapevine
Pierce’s disease (PD) of grapevine, caused by the bacterial pathogen Xylella fastidiosa (Xf), had led to significant crop losses in vineyards throughout California. An interesting observation about PD is that the disease appears to be limited to warmer climates, and that vines subjected to colder temperatures over the winter are “cured” of the disease by the next growing season. Very little is understood about this phenomenon except that it most likely involves many factors, included susceptibility of the pathogen to cold temperatures, and physiological response of different grapevine varieties to cold and to Xf infection. We will investigate the cold response of Xf using existing mutants in bacterial cold shock proteins and gene expression profiles created by RNA sequencing of Xf under cold stress. We also will investigate differences in winter-curing of Xf from different table grape varieties using cold treatment of Xf-inoculated vines and plant immune response assays.