Research Interest:
My laboratory is interested in understanding molecular basis of innate immune signaling
in plants. Salicylic acid (SA) mediated innate immune pathway is one of the major
pathways by which plants defend itself against microbial pathogens. Plants resisting
pathogen attack produce high amounts of salicylic acid which leads to activation of
defense pathways. How the SA activates defense signaling pathways is not entirely
clear? To understand this, several SA-binding proteins have been identified.
One such protein is a 29 kDa protein, salicylic acid binding protein 2 (SABP2)
which binds SA with high affinity (Kd=~90 nM). SABP2 is an esterase which catalyzes
the conversion of methyl salicylate (MeSA) to the active SA. Plants synthesize high
levels of MeSA while resisting pathogen attack. Three dimensional structure analysis
of SABP2 in complex with SA shows that SA binds in the active site of the SABP2. This
binding inhibits the enzymatic activity of SABP2 which stops the conversion of MeSA
to SA. Plants continue to make MeSA which is not only travels to other parts of the
plant but also to neighboring plants. SABP2 in the healthy parts of the plant catalyzes
the conversion of MeSA into SA which turns on the defense pathway and plant exhibits
systemic acquired resistance (SAR). RNAi-mediated silencing of SABP2 in tobacco rendered
the plant more susceptible to pathogen attack and it lost its ability to mount the
systemic acquired resistance (SAR) response. These RNAi plants were also compromised
in expression of defense genes.
Recent studies suggest that methyl salicylate is the long sought mobile signal
for plant innate immunity (SAR) which the scientists have been searching for more
that five decades (News). To further understand the role of SABP2 in plant defense
signaling and other physiological processes we are taking a combination of molecular
and biochemical approaches. Dr. Kumar's Laboratory Webpage
Courses:
- Biochemistry of Metabolism (BIOL 4167/5167)
- Plant Physiology (BIOL 4767/5767)
- Seminar (BIOL 5700)