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

Yang, L. and R. S. Poethig (2012). Mutations in the GW-reeat protein SUO reveal a developmental function for miRNA-mediated translational repression in Arabidopsis. Proc. Natl. Acad. Sci 109:315-320.

Earley, K. W. and R. S. Poethig (2011). Binding of the Cyclophilin 40 ortholog SQUINT to HSP90 protein is required for SQUINT function in Arabidopsis. J. Biol. Chem. 286: 38184-38189.

Wang, J-W., Park, M. Y., Wang, L-J., Koo, Y., Chen, X-Y., Weigel, D. and R. S. Poethig (2011) miRNA control of vegetative phase change in trees. PLoS Genetics 7:e1002012.

Willmann, M. R. and R. S. Poethig (2011) The effect of the floral repressor FLC on the timing and progression of vegetative phase change in Arabidopsis. Development 138: 677-685.

Yang, L., Conway, S. R. and R. S. Poethig (2011). Vegetative phase change is mediated by a leaf-derived signal that represses the transcription of miR156. Development 138: 245-249.

Poethig, R. S. (2010). The past, present, and future of vegetative phase change. Plant Physiol. 154: 541-544.

Earley, K. W., Smith, M. R., Weber, R., Gregory, B. D. and R. S. Poethig (2010) An endogenous F-box protein regulates ARGONAUTE1 in Arabidopsis. Silence 1: 15.

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 137:113-122.

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

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.

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.

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.

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.

education

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