Plants change as they develop. Some of these changes occur gradually over a long period of time, whereas others occur quickly, often resulting in major changes in shoot morphology. This latter phenomenon is termed phase change, and is the primary focus of our research. We are particularly interested in the juvenile-to-adult transition, also known as vegetative phase change. This transition precedes flowering, and is characterized by changes in shoot architecture and patterns of cellular differentiation, by an increase in reproductive competence, and by changes in a variety of physiological processes. Vegetative phase change is promoted by a group of plant-specific transcription factors (SBP/SPL proteins), whose expression is repressed during the juvenile phase by the miRNAs, miR156 and miR157. Vegetative phase change occurs when the levels of miR156/miR157 decline, leading to an increase in the abundance of SBP/SPL proteins. We are studying how the temporal expression pattern of miR156/miR157 is regulated, and how these miRNAs produce the morphological and physiological changes associated with vegetative phase change
We work primarily with Arabidopsis thaliana, but are also exploring the mechanism and evolution of vegetative phase change in the Acacieae, a pantropical family of nitrogen-fixing trees that includes species that do, and do not, undergo vegetative phase change. Our analysis of a group of Australian Acacias that do not undergo vegetative phase revealed that this phenotype is associated with a change in the expression pattern of miR156, and we are working to determine the genetic basis of this change. We are also studying the function of miR156 in the ant-Acacias of Central America, which produce a suite of morphological traits (swollen thorns, extra-floral nectaries, Beltian bodies) that facilitate their mutualistic relationship with ants.
A third area of interest is the development of genetic tools for Arabidopsis thaliana. We recently produced a set of transgenic lines (Traffic Lines) that significantly increase the speed and decrease the cost of many common tasks in genetic analysis. We are currently developing a set of Traffic lines that will allow investigators to monitor the segregation of 1 mB segments across the entire genome, and identify recombination events within these regions.
Biology 17: The Biology of Food
Biology 101: Introductory Biology
Biology 540/CAMB541: Genetic Analysis
He, J, Xu, M., Willmann, M. R., McCormick, K., Hu, T., Yang, L., Starker, C. G., Voytas, D. F., Meyers, B. C., and R. S. Poethig (2018). Threshold-dependent repression of SPL gene expression by miR156/miR157 controls vegetative phase change in Arabidopsis thaliana. PLoS Genetics 14(4): e1007337
Xu, M., Hu, T., and R. S. Poethig (2018). ACTIN-RELATED PROTEIN6 promotes the transcription of MIR156A and MIR156C by facilitating the deposition of H3K4me3. Development 145: dev152868. doi:10.1242/dev.152868
Guo, C., Xu Y., Shi, M., Lai,Y.,Wu, X.,Wang, H., Zhu, Z.,Poethig, R. S.,and G. Wu (2017) Repression of miR156 by miR159 regulates the timing of the juvenile-to-adult transition in Arabidopsis. Plant Cell 29:1293-1304.
Xu, M., Hu, T., Zhao, J., Park, M-Y, Earley, K.W., Wu, G., Yang, L., R. S. Poethig (2016). Developmental functions of miR156-regulated SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) genes in Arabidopsis thaliana. PLoS Genetics 12(8): e1006263
Xu, M., Hu, T., Smith, M. R. and R. S. Poethig (2016). Epigenetic regulation of vegetative phase change in Arabidopsis. Plant Cell 28: 28-41.
Poethig, R. S. (2016). Ian Sussex: simple tools, clever experiments and new insights into plant development. Development 143: 3224-3225.
Xu, Y., Guo C., Zhou, B., Li, C., Wang H., Zheng B., Ding H., Zhu Z., Peragine A., Cui Y., Poethig, R. S. and G. Wu (2016). Regulation of Vegetative Phase Change by SWI2/SNF2 Chromatin Remodeling ATPase BRAHMA. Plant Physiol. 172: 2416-2428.
Fouracre, J. P. and R. S. Poethig (2016) The role of small RNAs in vegetative shoot development. Curr. Op. Plant Biol. 29: 64-72.
Wu, G., Rossidivito, G., Hu, T., Berlyand, Y., and R. S. Poethig (2015). Traffic lines: new tools for genetic analysis in Arabidopsis thaliana. Genetics 200: 35-45
Gillmor, C. S, Silva-Ortega, C. O., Willmann, M. R., Buendîa-Monreal, M., and R. S. Poethig (2014). The Arabidopsis Mediator CDK8 module genes CCT (MED12) and GCT (MED13) are global regulators of developmental phase transitions. Development 141:4580-4589
Poethig, R. S. (2013) Vegetative phase change and shoot maturation in plants. In: Current Topics in Developmental Biology 105: 125-152
Yang, L., Xu, M., Koo, Y., He, J., and R. S. Poethig (2013). Sugar promotes vegetative phase change in Arabidopsis thaliana by repressing the expression of MIR156A and MIR156C. eLife 2:e00260
Yang, L. and R. S. Poethig (2012). Mutations in the GW-repeat 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.