Sorina Popescu

We are interested to study the function of proteins and how they assemble in complexes and pathways to carry on biological processes. Specifically, we study signal transduction pathways and gene regulatory mechanisms in the context of plant biotic interactions. For this, we have developed functional protein microarrays for the model plant system Arabidopsis thaliana (Popescu , Popescu 2007, Popescu et al. 2007).

Protein Microarrays

Protein microarrays represent a novel technology for the unbiased, large scale characterization of molecular interactions. They have been used for a wide variety of applications such as the study of enzyme-substrate, protein-protein, and protein-nucleic acid interactions, profiling antibody specificity, and searching for protein posttranslational modifications.

To generate functional protein microarrays (FPAs) we employ the recently developed Arabidopsis tagged ORF expression collection (ATEC). At the moment ATEC contains approximately one third of the Arabidopsis genome, in two years it will encompass more than half of the genome. To produce purified proteins for microarray printing we are using the N. benthamiana transient expression system, optimized for large-scale protein production. FPAs once generated in our lab, are used in various types of biochemical assays. Our work has been featured in the Journal of Proteome Research (Cottingham, K., 2007) and Analytical Chemistry (Griffiths, J., 2007).

Analysis of CaM and CML substrates on FPAs

Calmodulin (CaM) represents an essential regulatory protein conserved in all eukaryotes, which binds calcium and controls fundamental biological processes. Plants contain a large family of calmodulins and CaM-like proteins (CMLs) with functions in stress response and development.

Using FPAs with over 1,000 protein preparations, we have identified substrates of seven Arabidopsis CaM and CML protein isoforms. Several of the previously known substrates and a number of novel CaM-interacting proteins were found to interact with CaMs on FPAs. Our work generated the first experimentally-based plant protein interaction network that will aid in formulating new hypothesis on calmodulins role in the cell (Popescu, Popescu, Bachan, Zhang, Seay, Gerstein, Snyder and Dinesh-Kumar 2007). Currently we are expanding this analysis to include other plant proteins with roles in signal transduction.

Identification of signaling components in MAP kinase pathways

In a recent work, we have used FPAs containing more than 2000 proteins to study signaling through mitogen-activated protein kinases (MPKs). With over 60 MKKKs, 20 MKKs and at least 20 MPKs, the signaling transduction networks in Arabidopsis are immensely complex. To decipher them, we need to understand how signaling molecules associate with one another to transmit information and to identify the downstream substrates that are targeted by these pathways. These problems have been difficult to resolve because of cellular interactions, and the large number of genes with overlapping or redundant functions.

Our study revealed known and new signaling modules encompassing 570 MPK phosphorylation substrates for ten activated MPKs. MPK phosphorylated mostly transcription factors that regulate development, defense and stress responses (Fig. 1). We identified a subset of activated and wild type MKKs that induced HR-like death indicating a possible role for these MKKs in the regulation of cell death. The MPK phosphorylation network generated in this study is a comprehensive resource to experimentally analyze MPK signaling systems (Fig. 2) (Popescu 2009).

Attention: Position available:

Highly motivated individuals interested in applying for a Post-doctoral position in our lab, please submit the CV and a cover letter detailing research interests and career goals.

Boyce Thompson Insititute for Plant Research
Attention Sorina Popescu
Tower RD
Ithaca, NY 14853-1801 U.S.A.

Lab Members

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