James Umen, Ph.D.

Associate Member
Donald Danforth Plant Science Center
Adjunct Professor
Biology

Plant and Microbial Biosciences Program
Molecular Genetics and Genomics Program

  • 314-587-1689

  • Danforth Plant Science Center, 975 N. Warson Rd.

  • jumen@danforthcenter.org

  • http://umenlab.org/

  • evolution, cell biology, developmental biology, size control, cell division, sexual dimorphism

  • Cell growth, size control and evolution of sex in Volvocine algae

Research Abstract:

I have broad interests that merge the fields of cell biology, developmental biology and evolution. My laboratory utilizes the unique properties of the model green algae Chlamydomonas reinhardtii and its multicellular relative Volvox carteri to investigate cell size homeostasis, cell division and sexual dimorphism. Chlamydomonas and Volvox are established model organisms, but their combined potential to address fundamental questions in evolution and development is just starting to be realized. In Chlamydomonas the retinoblastoma (RB) tumor suppressor pathway is a key regulator of cell size homeostasis and cell cycle progression. Our work has uncovered new aspects of this pathway and its inputs that impact our understanding of eukaryotic size sensing and cell cycle control. Our research in Chlamydomonas is complemented by a second project on the evolution of sex. A conserved evolutionary transition that accompanied multicellularity in many lineages, including Volvocine algae, was the emergence of oogamy (egg/sperm mating systems). Oogamy requires that cell size control and gamete differentiation coevolve under the control of a mating locus or sex chromosome. The use of new high throughput sequencing methods and genomics combined with traditional developmental genetics has allowed us to make rapid progress in understanding the evolutionary dynamics of sex determination in Volvox that begins to shed light on the origins of oogamy. Our two major projects are connected at multiple levels by the involvement of the RB pathway and cell size control in Volvox developmental patterning and differentiation. We have recently begun a third project on photosynthetic growth control that aims to understand how photosynthetic cells regulate their metabolism under the control of externally supplied versus internally fixed carbon. Work in this area has uncovered a link between TOR (Target of Rapamycin) kinase and lipid metabolism that affects the tradeoff between cell growth, carbon source and lipid accumulation. This work holds promise for obtaining a better understanding of the carbon source/sink dichotomy in green organisms and for the development of improved algal strains for biofuel production.

Selected Publications:

Couso, I., Evans, B. S., Li, J., Liu, Y., Ma, F., Diamond, S., et al. (2016). Synergism between Inositol Polyphosphates and TOR Kinase Signaling in Nutrient Sensing, Growth Control, and Lipid Metabolism in Chlamydomonas. The Plant Cell, 28(9), 2026–2042. http://doi.org/10.1105/tpc.16.00351

Matt, G., & Umen, J. G. (2016). Volvox: A simple algal model for embryogenesis, morphogenesis and cellular differentiation. Developmental Biology. http://doi.org/10.1016/j.ydbio.2016.07.014

Hamaji, T., Mogi, Y., Ferris, P. J., Mori, T., Miyagishima, S., Kabeya, Y., et al. (2016). Sequence of the Gonium pectorale Mating Locus Reveals a Complex and Dynamic History of Changes in Volvocine Algal Mating Haplotypes. G3 (Bethesda, Md.), 6(5), 1179–1189. http://doi.org/10.1534/g3.115.026229

Hamaji, T., Lopez, D., Pellegrini, M., & Umen, J. G. (2016). Identification and Characterization of a cis-Regulatory Element for Zygotic Gene Expression in Chlamydomonas reinhardtii. G3 (Bethesda, Md.), 6(6), 1541–1548. http://doi.org/10.1534/g3.116.029181

Hamaji, T., Mogi, Y., Ferris, P. J., Mori, T., Miyagishima, S., Kabeya, Y., et al. (2016). Sequence of the Gonium pectorale Mating Locus Reveals a Complex and Dynamic History of Changes in Volvocine Algal Mating Haplotypes. G3 (Bethesda, Md.), 6(5), 1179–1189. http://doi.org/10.1534/g3.115.026229

Li, Y., Liu, D., Lopez-Paz, C., Olson, B. J., & Umen, J. G. (2016). A new class of cyclin dependent kinase in Chlamydomonas is required for coupling cell size to cell division. eLife, 5, 2104. http://doi.org/10.7554/eLife.10767

Lopez, D., Hamaji, T., Kropat, J., De Hoff, P., Morselli, M., Rubbi, L., et al. (2015). Dynamic Changes in the Transcriptome and Methylome of Chlamydomonas reinhardtii throughout Its Life Cycle. Plant Physiology, 169(4), 2730–2743. http://doi.org/10.1104/pp.15.00861

Zones, J. M., Blaby, I. K., Merchant, S. S., & Umen, J. G. (2015). High-Resolution Profiling of a Synchronized Diurnal Transcriptome from Chlamydomonas reinhardtii Reveals Continuous Cell and Metabolic Differentiation. The Plant Cell, 27(10), 2743–2769. http://doi.org/10.1105/tpc.15.00498

Cross, F. R., & Umen, J. G. (2015). The Chlamydomonas cell cycle. The Plant Journal, 82(3), 370–392. http://doi.org/10.1111/tpj.12795

Geng, S., De Hoff, P., & Umen, J. G. (2014). Evolution of Sexes from an Ancestral Mating-Type Specification Pathway. PLoS Biology, 12(7), e1001904–16. http://doi.org/10.1371/journal.pbio.1001904

Last Updated: 11/1/2016 11:51:17 AM

(a) Chlamydomonas cells (b) vegetative Volvox (c,d) sexual female and male Volvox
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