Dennis C. Gross

Professor, Department of Plant Pathology and Microbiology, Texas A&M University, 2009-present.

Professor and Head, Department of Plant Pathology and Microbiology, Texas A&M University, 2001-2009.

Chair, Department of Plant Pathology, Washington State University, 1999-2000.

Professor and Plant Pathologist, Department of Plant Pathology, Washington State University, 1979-2000.

My research is focused on Pseudomonas syringae pv. syringae, an aggressive colonizer of plant surfaces, as a model system to explore the influence of environmental effects, microbial interactions, and various pathological features, including host specificity, on ecological success of a major bacterial pathogen. The prevalence and importance of diseases caused by P. s. pv. syringae and other bacteria attest to the lack of effective control procedures. An understanding of the physiological, biochemical, and genetic determinants involved in initiation and establishment of disease is critical for developing new approaches to disease control.

P. s. pv. syringae B728a is a highly versatile pathogen that forms both acute infections of plants as well as long-term associations as bacterial aggregates that may be considered to embody “chronic” resident associations with plants. The molecular basis of how the bacterium switches from a resident epiphytic existence to an acute infectious agent is complex requiring the interaction of multiple virulence factors and associated secretion systems. In my laboratory, genetic studies of P. s. pv. syringae yielded important information about toxin production and its relationship to pathogenicity. For example, analysis of a 180 kb DNA region revealed that the syringomycin gene cluster lies adjacent to the syringopeptin gene cluster on the bacterial chromosome, and together they compose 2.2% of the genome to constitute a genomic island not found in the genomes of related pathovars. Consequently, we are now at a phase where the regulatory hierarchy can be described that controls expression of factors necessary for both acute and chronic associations of P. s. pv. syringae with plant hosts. My research projects are exploiting the B728a genome sequence to (A) characterize what appears to be a new secretion system that was discovered only recently to occur in medically important bacteria, and (B) define major regulons that contribute to epiphytic fitness and pathogenicity. My research program also includes studies aimed at detection and control of major plant pathogens of crops grown in Texas. These studies contribute to the overall goal of enhancing agricultural competitiveness in a global market.