R. Scott Poethig, Ph. D. Professor of Biology Ph.D., Yale University, 1980 103E Carolyn Lynch Laboratory Department of Biology University of Pennsylvania Philadelphia, PA 19104 USA V +1 215 898.8915 F +1 215 898.8780 E spoethig@sas.upenn.edu

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research : publications : education

genetic regulation of plant morphogenesis The morphology and physiology of a plant shoot change during development. Some of these changes are gradual, whereas others occur quickly at predictable times in development. This latter phenomenon is termed phase change, and is the primary focus of research in my laboratory. We are particularly interested in the transition from the juvenile to the adult phase of vegetative development (vegetative phase change). A microarray and high-throughput sequence analysis of the mRNA and small RNA content of leaves from different positions on the shoot in flowering and non-flowering plants has provided us with an unprecedented picture of the changes in gene expression that occur during shoot development. This large dataset is currently being mined for genes that may play important regulatory roles in this process. In parallel with this molecular approach, we are conducting a genetic analysis of vegetative phase change. This latter approach has revealed that vegetative phase change is regulated by two temporally-expressed miRNAs, miR156 and miR172. These miRNAs regulate multiple members of two families of plant-specific transcription factors--the SBP/SPL and AP2-like families. We are working to define the factors responsible for the temporal expression of miR156 and miR172, the developmental functions of their SBP/SPL and AP2-like targets, and the structure of the pathways in which these genes operate. Variation in leaf shape and the production of abaxial (yellow) and adaxial (red) trichomes along the length of the Arabidopsis shoot.   Because miRNAs and other classes of endogenous small RNAs play critical roles in vegetative phase change, screens for mutations that affect this process often identify genes that are generally required for small RNA biogenesis and function. When we identify genes whose function in these processes has not been previously described, we take the time to characterize their activity. This approach led to the discovery of trans-acting siRNAs and the unusual mechanism by which they are generated, and continues to provide new insights into the mechanisms by which small RNAs operate in plants.   polarity In plants, the specification of dorsiventral polarity in lateral organs is linked to the specification of radial polarity in the shoot. Genes involved in this process have been identified by screening for mutations that affect the expression pattern of transgenic line that expresses Green Fluorescent Protein solely in the peripheral/abaxial domain of the shoot. These include mutations that produce an expansion of the central domain, and mutations that perturb the location of the boundary between the adaxial and abaxial domains. Studies to determine the molecular and developmental functions of the genes identified in this screen are in progress. Stereomicroscopic (left) and confocal (right) image of an Arabidopsis embryo with a transgene that is expressed in the abaxial domain of the shoot.

recent publications

Gillmor, C. S., Park, M. Y., Smith M. R., Pepitone R., Kerstetter R. A., and R. S. Poethig (2009). The MED12-MED13 module of mediator regulates the timing of embryo patterning in Arabidopsis. Development (in press)

Wu G., Park, M. Y., Conway S. R., Wang J-W., Weigel D. and R. S. Poethig (2009). The sequential action of miR156 and miR172 regulates developmental timing in Arabidopsis. Cell 138: 750-759.

Yamaguchi A., Wu M-F, Yang L., Wu G., Poethig R. S., and D. Wagner (2009). The microRNA-regulated SBP-box transcription factor SPL3 is a direct upstream activator of LEAFY, FRUITFULL, and APETALA1. Dev. Cell 17: 268-278.

Poethig, R.S. (2009). Small RNAs and developmental timing in plants. Curr. Op. Gen. Dev. 19: 374-378.

Smith M. R., Willmann M. R., Wu G., Moller B., Weier D. and R. S. Poethig (2009). Cyclophilin40 is required for miRNA activity in Arabidopsis. Proc. Natl. Acad. Sci. 106: 5424-5429.

Wu, G., Lin, W-c, Huang T., Poethig R. S., Springer,P. S., and R. A. Kerstetter (2008). KANADI1 regulates adaxial-abaxial polarity in Arabidopsis by directly repressing the transcription of ASYMMETRIC LEAVES2. Proc. Natl. Acad. Sci. 105: 16392-16397

Willmann, M. R. and R. S. Poethig (2007). Conservation and evolution of miRNA regulatory programs in plant development. Curr. Op. Plant Biol. 10: 503-511.

Poethig, R. S., A. Peragine, M. Yoshikawa, C. Hunter, M. Willmann and G. Wu (2006). The function of RNAi in plant development. Cold Spring Harbor Symp. Quant. Biol. 71: 165-170.

Wu, G and R. S. Poethig (2006). Temporal regulation of shoot development in Arabidopsis by miR156 and its target SPL3. Development 133: 3539-3547.

Hunter, C, M. Willmann, G. Wu, M. Gutierrez-Nava and R. S. Poethig (2006). Trans-acting siRNA-mediated repression of ETTIN and ARF4 regulates heteroblasty in Arabidopsis. Development 133: 2973-2981.

Yoshikawa, M., Peragine, A., Park, M. Y. and R. S. Poethig (2005) A pathway for the biogenesis of trans-acting siRNAs in Arabidopsis. Genes & Dev. 19: 2164-2175.

Park, M. Y., Wu, G., Gonzalez-Sulser, A., Vaucheret, H. and R. S. Poethig (2005) Nuclear processing and export of microRNAs in Arabidopsis. Proc. Natl. Acad. Sci. 102: 3691-3696.

Willmann, M. R. and R. S. Poethig (2005) Time to grow up: the temporal role of small RNAs in plants. Curr. Op. Plant Biol. 8: 548-552.

Peragine, A., Yoshikawa, M., Wu, G., Albrecht, H. L. and R. S. Poethig (2004) SGS3 and SGS2/SDE1/RDR6 are required for juvenile development and the production of trans-acting siRNAs in Arabidopsis. Genes & Dev. 18: 2368-2379.

education

Ph.D., Yale University, 1980
M.A., Yale University, 1976
B.A., College of Wooster, 1974