While most plants are resistant to most pathogens, when disease does occur, it can be devastating to farmers and consumers. Pesticides are often employed in an attempt to limit spread, further adding to the total cost of disease. The Bart lab will focus on exploring natural genetic diversity and exploiting identified phenotypic traits for sustainable crop improvement. The 21st century is a transformative time to be a geneticist with an affinity for agriculture because modern molecular biology tools can be readily applied to genetically intractable organisms. The disease triangle of plant pathology tells us that the host, the pathogen as well as the environment affect the observed severity of a given disease.
On the host side, the Bart lab is working to identify resistance genes for use in crop improvement. A major limitation facing this type of crop improvement is the slow and laborious nature of traditional breeding. Next-generation sequencing technologies can be applied rapidly to any organism and can increase the speed at which genetic loci are identified. The majority of identified resistance genes contain nucleotide-binding site and leucine rich repeat domains. The lab is working to develop computational methods of using genomics data to identify candidate resistance genes. These candidates will be validated through transient assays and then used directly for crop improvement. In addition, future research will aim to tease out the molecular mechanisms governing resistance gene function.
One the pathogen side, the Bart lab aims to identify conserved components of the microbial arsenal, as resistance genes generally target proteins involved in pathogen virulence. Targeting the most highly conserved virulence components with resistance strategies will lead to durable resistance in the field. Here again we can apply next generation sequencing to rapidly construct draft genomes for hundreds of bacterial isolates. Genes involved in virulence are computationally predicted and used as molecular probes for cognate resistance genes. A sub-class of bacterial virulence determinants known as type three effectors (T3Es) are secreted directly into the plant cell via the type three secretion system. Many T3Es contain eukaryotic domains that allow them to function inside the host cell. Transcription activator-like (TAL) effectors, for example, are able to bind promoter elements and direct transcription of host genes. TAL effectors have received attention recently for their potential in genome editing. Research in the Bart lab aims to understand the molecular function of these effectors as well as to characterize their respective roles in overall virulence.
Many bacterial diseases require humid climates to establish infection. A long-term goal of the Bart laboratory is to understand the impact of environmental changes on the interaction between pathogens and their hosts. Examples of important environmental changes include modulations in temperature and humidity throughout the growing season or as a result of global climate change, new cultivar introduction, and chemical inputs.