Research
Molecular
Biology of Plant-Pathogen Interactions
How
microbial pathogens cause diseases in higher eukaryotes
is a major unresolved question in biology. Our research
is focused on the interaction between Arabidopsis thaliana
and Pseudomonas syringae. In this model interaction,
both the host and the pathogen are genetically and genomically
amenable, making it a fascinating system for dissecting
the molecular details of bacterial virulence, host defense,
and host-pathogen co-evolution. We are currently pursuing
three lines of research: (1) We study the hrp gene-encoded
type III protein secretion system, which injects bacterial
virulence proteins directly into the host cell. (2)
We investigate host proteins and pathways targeted by
P. syringae virulence proteins. (3) We explore novel
strategies to produce disease-resistant plants, based
on our basic understanding of the Arabidopsis-P. syringae
interaction. Our research is driven by scientific questions.
All available and proper technologies are used to solve
specific questions. This lab provides a supportive environment
for students and postdocs to gain experience in molecular
biology, genetics, cell biology, and biochemistry with
a specialization in plant-microbe interactions.
Bacterial
type III protein secretion and plant host susceptibility
to disease
The
ability of P. syringae to cause disease in susceptible
plants or to elicit the hypersensitive response (HR,
a rapid plant cell death response associated with plant
resistance) in resistant plants is genetically controlled
by a cluster of highly conserved bacterial genes, known
as hrp genes. Research from our laboratory is contributing
to the elucidation of the structure and function of
hrp genes. It is now clear that most hrp gene products
are involved in the assembly of a type III secretion
apparatus in the interface between the infecting bacteria
and plant cells. Bacterial virulence proteins (type
III effector proteins) traverse the type III secretion
apparatus from bacteria directly into the plant cell
interior to affect plant physiology, leading to disease.
The molecular mechanism of the Hrp-mediated type III
protein secretion from bacteria to plant cells is poorly
understood and is an exciting area of research in the
fields of microbiology and plant-pathogen interactions.
We found that a key feature of this secretion system
is the construction of a surface filamentous appendage-the
Hrp pilus. Accumulating evidence suggests that the Hrp
pilus functions as a conduit (tube) for transporting
type III effector protein into the host cell.
Host
targets of P. syringae type III effector proteins
What
do P. syringae type III effector proteins do inside
the Arabidopsis cell? What host proteins and pathways
are targeted by these bacterial ‘smart bombs?”
Answering these questions is fundamental to our understanding
of disease development. This is an exciting new area
in the field of molecular plant-pathogen interactions.
We are using transgenics, global gene profiling, protein
structure, and yeast two-hybrid protein trap methods
to reveal the physiological targets inside the Arabidopsis
cell of P. -syringae type III effector proteins.
Biotechnology
Producing
disease-resistant crop plants is a major goal of the
basic research on plant-pathogen interactions. To this
end, we are producing plants expressing nonfunctional
type III effectors to interfere with the normal interaction
of functional type III effectors and their host targets.
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