The plant-microbe pathosystem constitutes a very complex biological network in which the molecular players from both the pathogen and the host engage in a battle for dominance. Specialized pathogens have evolved suites of molecules called effectors that modulate host cell physiology and support parasitism. Over the past decades, a plethora of literature has documented the molecular mechanisms that underlie the induction of effective immune responses and subversion of effector-mediated host defenses. However, a key unresolved question is how pathogens alter cellular metabolism, including manipulation of the source-sink relationships, to acquire nutrients. This interdisciplinary project extends significantly beyond wet-lab techniques by integrating both biology and the rapidly evolving field of computer science for the advancement of research, education, and community-based scientific engagement. Mechanistic understanding of effector-mediated perturbations to mobilize sugars from the central vacuole will be pursued. Elucidating how pathogen infection modulates the global transcriptional dynamics and alters the flow of biological information is of prime focus. Equally paramount, cross-talk between metabolic, hormonal, circadian and immune signaling pathways, involving signals from pathogenic and non-pathogenic bacterial strains, will be revealed. Situated in the heart of Alabama, at a nationally recognized university for diversity, this project's scope extends into educational avenues as students in advanced level genomics courses will gain experience with relevant bioinformatic analyses, urban high school teachers in the PI's-led BioTeach program will gain exposure to the genetic innovations of today, and zealous recruiting efforts will seek to engage neighboring HBCU-minority students.
The central framework of this proposal, understanding how plant pathogens acquire sugars through the virulence activities of their effectors, presents a substantial advancement over the previously limiting dimensions of a one pathogen: one protein analysis approach. Specifically, this project is focused on a pathogen effector, HopD1, that physically interacts with a set of host proteins forming a functional module, termed 'vacuolar invertase (Vac-INV) module.' The mechanisms by which HopD1 perturbs the Vac-INV module to mobilize sugars stored in the central vacuole while slowing down the resorption of apoplastic sugars into the host cell will be investigated. HopD1's immune response suppression through interference of a conserved aquaporin-mediated stomatal regulation mechanism will also be investigated. Based on the in silico modeling of Vac-INV?dependent transcriptional circuits, a high resolution global dynamic transcriptional regulatory network in plant-pathogen interactions will also also constructed. Having already developed a web-based interface, OOCEAN, for promoter and bioinformatics analyses, this project will continue to extend its utility in the fast-evolving world of Systems Biology. Novel network biology-based analyses will help obtain a broad understanding of how single effectors simultaneously target different branches of plant immunity and metabolism for the pathogen's advantage. This work will also result in a system that can be applied to other important questions pertaining to plant defense and metabolism as well. Collectively, this systems-level project will solidify global understanding of effector-host interactions, effector-mediated perturbations, and subsequently, dynamic transcriptional regulation.
