Archibald Lab Research

The central focus of research in the Archibald Lab is to gain insight into the origin and evolution of eukaryotic genomes using microscopic algae (microalgae) as model organisms. Animals (including humans) and plants are perhaps the most obvious eukaryotic life forms, but the vast majority of eukaryotic diversity lies within the microscopic realm. For this reason, microbial eukaryotes are extremely poorly understood, in particular, with respect to their molecular biology. Using a comparative genomics approach, the lab is interested in (1) elucidating some of the pivotal molecular and biochemical events that have shaped the evolution of eukaryotic cells, (2) understanding the evolutionary relationships amongst eukaryotic microbes and (3) understanding how eukaryotic genes, genomes and proteins change over time. Currently the main projects in the lab are as follows:

Secondary endosymbiosis and nucleomorph genome evolution:
The plastids (chloroplasts) of photosynthetic eukaryotes are the product of an ancient symbiosis between a heterotrophic eukaryote and a free-living cyanobacterium. It is widely believed that this process, known as primary endosymbiosis, occurred only once and that all plastids descend from a single common ancestor. However, plastids have also moved laterally amongst unrelated eukaryotic cells by secondary endosymbiosis, a process that has occured multiple times and has given rise to a staggering array of photosynthetic organisms (see Archibald 2005 IUBMB Life 57: 539- and references therein for review). The cryptophytes and chlorarachniophytes are two microalgal lineages that are of particular interest with respect to secondary endosymbiosis. Unlike all other secondary plastid-containing algae, these organisms have retained the nucleus of the eukaryotic endosymbiont in a highly derived form called a nucleomorph. The nucleomorph genomes of chorarachniophytes and cryptophytes are very fast evolving and are the smallest eukaryotic genomes known, having transferred most of their genetic material to the nuclear genome of their respective host cells. Within the two groups, nucleomorph genome size varies considerably from lineage to lineage. By studying the size, structure and coding capacity of nucleomorph genomes in a variety of chlorarachniophytes and cryptophytes we are trying to elucidate the fundamentals of eukaryotic genome evolution, endosymbiosis, gene transfer and genome reduction. We recently published the 572 Kbp genome of the cryptophyte Hemiselmis andersenii (Lane et al. 2007. Proc. Natl. Acad. Sci. U.S.A. 104, 19908-19913) which represents the first known case of a nuclear genome devoid of spliceosomal introns. Refer to our Publications page for recent papers in this area.

Nuclear genome sequences of cryptophytes and chlorarachniophytes:
The Archibald Lab is spearheading an effort to sequence the nuclear genomes of the cryptophyte Guillardia theta and the chlorarachniophyte Bigelowiella natans. The sequencing is being funded by the Community Sequencing Program of the Joint Genome Institute in Walnut Creek, California. Shortly after these genomes are sequenced, assembled and annotated, they will be available to the public through the JGI eukaryotic genomics web portal. You can learn more about this project here. Our main collaborators are the Gray, Keeling, McFadden, Apt, Beiko, Durnford, Green, Ishida and, Maier Laboratories. We are greatful to Karrie Barry for project management and James Bristow and the rest of the JGI-CSP for supporting this research.

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Funding

Diversity of plastids

Chlorarachniophytes

Cryptophytes and nucleomorphs

Hemiselmis andersenii nucleomorph

Last updated: September 15, 2008