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evolution, cell biology, developmental biology, homeostasis, cell division, sexual dimorphism

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Danforth Plant Science Center, 975 N. Warson Rd.



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 (eggsperm 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 is described briefly below and which is connected to lipid accumulation.

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James Umen

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Date Last Updated

11/10/2011 6:20 PM


Balsemão-Pires E, Jaillais Y, Olson BJ, Andrade LR, Umen JG, Chory J, Sachetto-Martins G. The Arabidopsis translocator protein (AtTSPO) is regulated at multiple levels in response to salt stress and perturbations in tetrapyrrole metabolism. BMC Plant Biol. 2011 11:108.
Olson BJSC, Oberholzer M, Li Y, Zones JM, Kohli H, Bisova K, Fang S-C, Meisenhelder J, Hunter T and Umen JG. Regulation of the Chlamydomonas cell cycle by a stable nuclearlocalized retinoblastoma tumor suppressor complex. Plant Cell 2010 22:3331-47.
Umen JG. Controlled chaos: New insights into genetically controlled asynchrony. Cell Cycle 2010 9(19) 3843-4. News and Views article.
Prochnik* S, Umen*‡ JG, Nedelcu A, Hallmann A, Miller S, Nishii I, Ferris P, Kuo A, Mitros T, Hellsten U, Chapman J, Simakov O, Rensing S, Terry A, Pangilinan J, Salamov A, Shapiro H, Lindquist E, Lucas S, Kapitonov V, Grigoriev I, Schmitt R, Kirk D, Rokhsar‡ D. Genomic Analysis of Organismal Complexity in the Multicellular Green Alga Volvox carteri. Science 2010 329:223-6. *Equal author contribution. ‡ Co-corresponding authors.
Ferris P, Olson BJSC, De Hoff PL, Douglass S, Diaz-Cano DC, Prochnik S, Geng S, Rai R, Grimwood J, Schmutz J, Nishii I, Hamaji T, Nozaki H, Pellegrini M and Umen JG. Evolution of an Expanded Sex Determining Locus in Volvox. Science 2010 328:351-4. PMCID: PMC2880461.

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Male Volvox with sperm packets

Research Image Url Research Images/James_Umen_6317.jpg

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Created at 11/10/2011 6:20 PM by DBBS_SP_SAPP
Last modified at 11/11/2011 9:08 AM by Kathryn Ruzicka