James Umen, Ph.D.

Associate Member
Donald Danforth Plant Science Center
Adjunct Professor

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:

We have broad interests that merge the fields of cell biology, developmental biology and evolution. We utilize the unique properties of the model green alga Chlamydomonas reinhardtii and its multicellular relatives including Volvox carteri to investigate questions at the interfaces of evolution, developmental biology, cell biology and metabolism. Current projects include:

Evolution of sex and sexual dimorphism.
Sexes and sexual dimorphism have fascinated evolutionary biologists since Darwin first developed the theory of sexual selection. Male-female dimorphism evolved from mating types in volvocine algae under the control of a complex mating locus and an associated transcription factor called MID from the RWP-RK family. We investigate how the MID network coevolved with volvocine algal sex chromosomes and sex determination mechanisms in the transition from mating types to sexes.

Origins and evolution of germ-soma differentiation.
One of the most common innovations in multicellular life is the separation of an immortal germ lineage from terminally differentiated somatic cells. The multicellular alga Volvox has evolved complete-germ soma differentiation under the genetic control of several key regulators including the putative transcriptional repressor, regA. We are investigating the targets of regA and how its expression causes terminal differentiation and senescence inn somatic cells.

Cell size homeostasis and the retinoblastoma (RB)tumor suppressor complex in Chlamydomonas.
Chlamydomonas cells divide by multiple fission and control size by modulating the number of divisions that a mother cell undergoes in each cycle. The RB protein complex is a key regulator of size control and is part of a size sensing pathway that includes upstream cyclin dependent kinases and a musashi-like RNA binding protein. We are developing methods to investigate how upstream regulators respond to cell size and the mechanisms by which the RB complex activates or represses cell cycle progression through non-transcriptional effects on chromatin.

TOR kinase and inositol polyphosphate signaling in the control of cell growth and carbon partitioning in Chlamydomonas.
Proliferating cells must integrate nutritional information with biosynthetic processes to maintain balanced growth. The target of rapamycin (TOR) protein kinase is a conserved growth regulator across eukaryotes. We recently found a novel interaction between TOR signaling and the inositol polyphosphate (InsP) biosynthetic pathway in Chlamydomonas. Mutants in the InsP kinase VIP1 are hypersensitive to TOR inhibition and have metabolic defects leading to increased neutral lipid accumulation. This finding has practical implications for engineering algae for biofuel production, and opens up a new avenue for investigating metabolism and carbon partitioning under the control of InsPs.

Selected Publications:

Geng S, Miyagi A, Umen JG. (2018) Evolutionary divergence of the sex-determining gene MID uncoupled from the transition to anisogamy in volvocine algae. Development, doi: 10.1242/dev.162537.

Matt GY, Umen JG. (2018) Cell-Type Transcriptomes of the Multicellular Green Alga
Volvox carteri Yield Insights into the Evolutionary Origins of Germ and Somatic
Differentiation Programs. G3 (Bethesda), 8(2):531-550. doi: 10.1534/g3.117.300253.

Hamaji, T., Kawai-Toyooka, H., Uchimura, H., Suzuki, M., Noguchi, H., Minakuchi, Y., Toyoda, A., Fujiyama, A., Miyagishima, S.-Y., Umen, J. G., and Nozaki, H. (2018) Anisogamy Evolved with a Reduced Sex-Determining Region in Volvocine Green Algae. Communications Biology, 1(1):247. doi:10.1038/s42003-018-0019-5.

Werth, E. G., McConnell, E. W., Gilbert, T. S. K., Couso Lianez, I., Perez, C. A., Manley, C. K., Graves, L. M., Umen, J. G., and Hicks, L. M. (2017) Probing the Global Kinome and Phosphoproteome in Chlamydomonas reinhardtii via Sequential Enrichment and Quantitative Proteomics. Plant J., 89(2):416-426. doi: 10.1111/tpj.13384.

López-Paz C, Liu D, Geng S, Umen JG. (2017) Identification of Chlamydomonas
reinhardtii endogenous genic flanking sequences for improved transgene
expression. Plant J., 92(6):1232-1244. doi: 10.1111/tpj.13731.

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

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

Last Updated: 7/25/2018 8:15:18 AM

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