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Dr. Maeli Melotto

Melotto

Assistant Professor of Biology
MAJOR AREA: Molecular Biology of Plant-Microbe Interactions
OFFICE: B29 Life Science
PHONE: 817-272-1122
LAB: B14 life Science
PHONE: 817-272-1112
FAX: 817-272-2855
melotto@uta.edu
 PhD: Michigan State University, East Lansing, MI (1999)

My research program is focused on two aspects of plant-pathogen interactions 1) to understand the mechanisms by which plants defend themselves against bacterial infection, and 2) to study virulence strategies evolved by bacterial pathogen to overcome plant defenses. My current work integrates plant genetics and pathology, genomics and bioinformatics to gain knowledge in the field of the plant innate immune system and bacterial pathogenesis.

Basal immunity in plants, much like innate immunity in animals, is activated by the recognition of pathogen-associated molecular patterns (PAMPs; the conserved molecules among microbes). The functional role of basal innate immunity in limiting bacterial infection has been unclear until recently. I have found that a major function of the PAMP-induced innate immunity is stomatal defense against bacterial entry into the plant tissue.

Opening and closure of stomata is controlled by environmental factors such as light, humidity, and CO2 concentration among others. It has been thought that stomata (unwittingly) provide ports for bacterial entry into internal tissues. Surprisingly, I discovered that stomata function as an active defense, closing in response to plant and human pathogenic bacteria, as well as purified PAMPs. Stomatal closure in response to these treatments requires several components of the plant innate immunity and abscisic acid signaling. Thus, stomata play a crucial role in restricting bacterial infection. The plant pathogen, but not the human pathogen Escherichia coli, is able to overcome stomatal defenses and re-open the stomata, thereby gaining entry to the intercellular spaces, ultimately leading to colonization and disease. To overcome stomate-based defense, the virulent Arabidopsis pathogen Pseudomonas syringae pv. tomato DC3000 has evolved the virulence factor coronatine (COR) to suppress stomatal closure.

My current research effort is geared towards uncovering this novel and crucial early host-bacterium interaction in the phyllosphere. The discovery of host-bacterium battles at stomata represents a significant conceptual advance in our understanding of not only bacterial pathogenesis and stomatal biology but also microbial ecology of plant and human pathogenic bacteria in the phyllosphere.