Sona Pandey

Dr. Pandey received a B.Sc. (Hons) in Chemistry and M.Sc. in Biotechnology from Banaras Hindu University, India. She received her Ph.D. in Life Sciences form Jawaharlal Nehru University, India. She worked as a research scientist in Center for Plant Molecular Biology, New Delhi, India before starting a post-doctoral career at the Pennsylvania State University, University Park, PA. Dr. Pandey joined the Donald Danforth Plant Science Center in April 2008 as an Assistant Member and Principal Investigator.

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Research

Plants show a phenomenal degree of adaptation and phenotypic plasticity in response to different environmental conditions. The focus of our research is to understand how plants perceive and respond to abiotic stress. Towards this we work with a class of evolutionary conserved proteins the heterotrimeric G-proteins and a plant hormone abscisic acid (ABA). ABA regulates almost all phases of plant growth and development, from seed dormancy and germination to leaf and fruit abscission. ABA is also the most important stress signal in plants, involved in response to both abiotic and biotic stresses.

Understanding of ABA-perception mechanisms is central to our knowledge of how ABA regulates these diverse processes. Almost all aspects of ABA signaling in plants are regulated by heterotrimeric G-proteins. Heterotrimeric G-proteins consisting of α, β and γ subunits are signal transducers in all eukaryotes. The G-proteins are positioned such in signaling pathways that they interact with upstream receptors as well as downstream effectors to combine signal-perception to signal-transduction. In humans, an extensive network of hundreds of receptors, and multiple G-protein subunits and downstream effectors regulate 1/3rd of all signaling pathways including vision, taste and olfaction. These signaling pathways are also targets of more than half of all pharmaceutical drugs. Plant G-proteins are similar to their mammalian counterparts with respect to the diverse signaling processes they regulate, but are significantly different in the number of classical G- protein components e.g. the fully sequenced genomes of Arabidopsis and rice has only one Gα subunit, one Gβ subunit and 2 Gγ subunits, in contrast to 23 Gα subunits, 5 Gβ subunits and 12 Gγ subunits found in humans. Few GPCR-like proteins are reported in plants compared to almost 800 known GPCRs in humans.

We have identified two highly homologous proteins in Arabidopsis that have G-protein coupled receptor- (GPCR-) like topology, and an inherent G-protein activity, and named them GPCR-Type G-protein (GTG1 and 2). The GTG proteins are plasma membrane localized ABA receptors. The main goal of this research is to understand the mechanism of action of GTG proteins in the context of known ABA signaling pathways in plants. Towards this, we are taking an interdisciplinary approach using tools from biochemistry, molecular biology, cell biology, genetics and proteomics to decipher:

1. the initial ABA-induced changes in GTG proteins and the roles of specific motifs involved in G-protein activity and ABA perception,
2. identification of GTG proteins’ interacting proteins and their role in ABA signal transduction
3. changes in protein profiles and post-translational modifications in gtg1gtg2 mutants that define signal transduction via GTG proteins.

We are also studying the roles of soybean G-proteins in regulating ABA and GA signaling, with respect to general and legume-specific growth and developmental processes. Our analysis of soybean sequences has identified four Ga, four Gb and six putative Gg subunits in its genome, predicting ninety-six possible heterotrimeric combinations and making it the most diverse G-protein network known to date in plants. Only two such combinations exist in Arabidopsis and rice. We are using molecular genetics, biochemistry, genomics, proteomics, protein-protein interactions, site-directed mutagenesis, and cell biology-based techniques to characterize the G-proteins at biochemical and molecular level with the long term goal of elucidating their role in regulating soybean growth and development.

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