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Marja Timmermans

Professor
Ph.D., Rutgers University, 1996

small RNA regulation, pattern formation, stem cell function, plant development

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Timmermans2013 Plants grow and develop organs, such as leaves, throughout their lifetime. The growing tips of plants contain a population of stem cells that serve as a persistent source of daughter cells from which new organs arise. A main objective of the research in the lab is to identify novel components in the gene networks that regulate plant stem cell activity and that distinguish indeterminate stem cells from their differentiating derivatives.

Our recent work showed that the Polycomb Repressive Complex2 mediates the epigenetic silencing of stem cell promoting genes during normal differentiation. We are taking a genomics approach to identify novel PRC2 targets and are investigating the dynamics of Polycomb-mediated gene silencing, a key question also in the mammalian stem cell field.

In addition, we are studying the role of small regulatory RNAs in stem cell regulation and developmental patterning. We previously showed that small RNAs are able to move from their source of biogenesis to create accumulation gradients. Computational modeling predicts that such small RNA gradients have morphogen-like activity and are uniquely suited to form stable and precisely defined target gene expression boundaries. Our current research efforts are aimed at testing this model, and at understanding the mechanisms via which small RNAs move from cell to cell and function as instructive signals to create developmental patterns. 

In our research, we take advantage of molecular genetic, genomic, biochemical and computational approaches. Moreover, we use Arabidopsis, maize and the moss Physcomitrella patens in our studies, as each model organism offers unique experimental advantages and because comparative studies provide an evolutionary perspective.


 

Selected Publications

Lodha, M., Marco, C.F., and Timmermans, M.C.P. 2013. The ASYMMETRIC LEAVES complex maintains repression of KNOX homeobox genes via direct recruitment of Polycomb-repressive complex2. Genes Dev. 27: 596–601.

Chitwood, D.H. and Timmermans, M.C.P. 2010. Small RNAs are on the move. Nature 467: 415–419.

Chitwood, D.H., Nogueira F.T.S., Howell, M., Montgomery, T.A. Carrington, J.C. and Timmermans, M.C.P. 2009. Pattern formation via small RNA mobility. Genes Dev. 23: 549–554.

Guo, M., Thomas, J., Collins, G., and Timmermans, M.C.P. 2008. Direct repression of KNOX loci by the ASYMMETRIC LEAVES1 complex of Arabidopsis. Plant Cell 20: 48–58.

Nogueira, F.T.S., Madi, S., Chitwood, D.H., Juarez, M.T., and Timmermans, M.C.P. 2007. Two small regulatory RNAs establish opposing fates of a developmental axis. Genes Dev. 21: 750–755.