James Umen,

PhD

Member, Enterprise Rent-a-Car Institute for Renewable Fuels and Joseph Varner Distinguished Investigator

An Early Interest in Science

Growing up in suburban Twin Cities, Jim Umen had an early interest in the natural world.

“I remember visiting the beach when I was 7 or 8 and loved exploring tidepools. Each one was a different little world populated with animals and seaweeds.”

During a short internship program in high school, he worked in a microbiology lab and cemented his interest in in biology. As an undergraduate, he became interested in cancer research, but in graduate school some mentors steered him toward microbial genetics and he found his calling. As a postdoc at Washington University, he became fascinated by a single-celled species of algae (Chlamydomonas) that has become a model species for understanding the biology of green algae.

Today, Jim Umen, PhD, is the Joseph Varner Distinguished Investigator at the Danforth Center and a member of the Enterprise Rent-a-Car Institute for Renewable Fuels. 

Why Algae?

An alga (plural algae) is defined in the dictionary as “a simple, nonflowering, and typically aquatic plant of a large group that includes the seaweeds and many single-celled forms.”

Jim laughs.

“That’s mostly right, but technically speaking, plants evolved from algae, not the other way around.” Unlike land plants which form a single related group of organisms, algal diversity encompasses multiple independent branches across the tree of life, with green algae (the closest algal relatives of land plants) being just one of these branches. Research on different groups of algae has helped to illuminate some of the most fundamental evolutionary processes that contribute to biodiversity and shape life on Earth.  

Sex and the Single Cell

Jim’s team is interested in fundamental scientific questions, such as the origins of separate male and female sexes. Plants, animals, some algae, and several other groups of organisms had single-celled ancestors which could mate and undergo genetic exchange (sex); but the mating partners were almost indistinguishable from one another. There was sex, but there were no sexes. Jim’s research on algae is helping to decipher the evolutionary transition from single cells with mating types to multicellular species with sexes in greater detail than is possible in any other group of organisms.

Another area of work in the Umen laboratory explores how cells make decisions about when to divide. Cells know exactly how big they should be, and when they grow to the appropriate size they undergo division. Some of the cellular switching mechanisms for turning division on and off are shared between algae and more complex organisms like plants and animals, adding biomedical relevance to the research.

The questions explored in the green algae studied by Umen’s lab shed light on breeding improved strains of algae, much the same way crop breeders improve plants. These improvements could contribute to commercial algal biofuels and other high-value bioproducts produced from algae.

On the importance of algae

"People don’t realize that oil is fossilized algae, just as coal is fossilized plants. Algae are incredibly efficient producers of oil."

Fun Facts

He loves foraging, fly-fishing, and cooking all cuisines. Sichuan Ma-Po Tofu is his signature dish.

On the importance of algae

"People don’t realize that oil is fossilized algae, just as coal is fossilized plants. Algae are incredibly efficient producers of oil."

Fun Facts

He loves foraging, fly-fishing, and cooking all cuisines. Sichuan Ma-Po Tofu is his signature dish.

Get in touch with James Umen

Research Team
Research Summary

The Umen laboratory investigates the genetics and cell biology of green algae to enable development of sustainable sources of biofuel and other high-value compounds.

James Umen

Principal Investigator, Member

Yi-Hsiang Chou

Postdoctoral Associate

Hunter Draffen

Lab Assistant

Patrick Ferris

Research Associate

Minglu Gao

Postdoctoral Associate

Sa Geng

Research Scientist

Dianyi Liu

Graduate Student

Zoee Perrine

Postdoctoral Associate

Sarah Rommelfanger

Graduate Student

Peipei Sun

Postdoctoral Associate

Dylan Wetzel

Laboratory Assistant

James Umen

Principal Investigator, Member

Yi-Hsiang Chou

Postdoctoral Associate

Hunter Draffen

Lab Assistant

Patrick Ferris

Research Associate

Minglu Gao

Postdoctoral Associate

Sa Geng

Research Scientist

Dianyi Liu

Graduate Student

Zoee Perrine

Postdoctoral Associate

Sarah Rommelfanger

Graduate Student

Peipei Sun

Postdoctoral Associate

Dylan Wetzel

Laboratory Assistant

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Using algae as a primary experimental system, Jim’s research is investigating cell size control, cell growth regulation and carbon partitioning, and evolution of multicellularity.

I maintain a diverse and interdisciplinary research program aimed at answering fundamental questions in eukaryotic cell biology, evolution and development using the green algae Chlamydomonas reinhardtii (Chlamydomonas) and Volvox carteri (Volvox), as well as some of their close relatives in the volvocine algal family. Green algae are the smallest and simplest members of the green plant lineage, and are an ecologically important group of organisms for their role in the global carbon cycle.  They are also excellent models for many areas of basic plant biology and for eukaryotic cell biology. Our research takes advantage of unique aspects of Chlamydomonas and Volvox to answer questions that can ultimately impact agriculture and human health. The most direct translational impacts of our work will be in algal biotechnology where cell size, growth metabolism, and oil composition are important yield traits, while our work on sexual cycles may enable development of breeding and improvement strategies for algal crop species.

Our work is in three main areas: 1. Cell size homeostasis and cell cycle control; 2. Cell growth control and carbon metabolism; and 3. Evolution of sexual dimorphism and germ-soma differentiation.  The three topics are described separately below, but there are technical and conceptual connections and synergies between them that we have exploited to advance our work in all three areas.

 

Cell Size Homeostasis and the RB Tumor Suppressor Pathway

Size homeostasis is a fundamental property of proliferating cells and is thought to be governed by cell size checkpoints. The multiple fission cell cycle of Chlamydomonas uncouples cell growth and division and allows us unique access to a size checkpoint mechanism. A key regulator of this checkpoint is the Chlamydomonas retinoblastoma (RB) tumor suppressor pathway, whose function in cell size and cell cycle regulation is a major focus of investigation.

 

Cell Growth Regulation in Photosynthetic Eukaryotes

Cell growth in eukaryotes requires the coordinate regulation of cytoplasmic biosynthetic processes with those in chloroplasts and mitochondria, semi-autonomous organelles that contain their own protein biosynthetic machinery. Chloroplasts from higher plants and green algae represent a large fraction of cellular biomass yet it is unknown how their growth is regulated with respect to cytoplasmic growth. The TOR (target of rapamycin) kinase signaling pathway is conserved in all eukaryotes where it functions as a nutrient-sensitive modulator of growth rates. We are using Chlamydomonas as a simple model for how TOR signaling contributes to coordinated growth control in photosynthetic eukaryotes.

 

Evolution of Developmental Complexity

Chlamydomonas reinhardtii belongs to a diverse clade of green algae, some of which have undergone a remarkable transition to multicellularity. The best-characterized of the multicellular relatives is Volvox carteri, a species that embodies many of the hallmarks of multicellular metazoans or plants. These include terminally differentiated somatic cells, reproductive stem cells, complex embryonic patterning, and formation of sexually dimorphic germ cells (eggs and sperm), none of which are present in its unicellular relative Chlamydomonas. Our current work is aimed at understanding the evolution of genetic networks that enabled the specification of germ and somatic cells as well as the relationship between sex determination genes, sex chromosomes and sexual dimorphism in Volvox.