Giardia lamblia is a human gut parasite, and a representative of the excavates, one of the earliest-branching of eukaryotic lineages. We explored the kinomes of three strains of Giardia, and two other excavates (Trichomonas vaginalis and Leishmania major) to peer back in time to the early evolution of eukaryotic protein kinases, and to see how the kinome may reflect Giardia's specialized cell cycle and parasitic lifestyle. Our main findings are published in Genome Biology, and through the KinBase database on this site: This work was a collaboration between the Gillin lab at UCSD (spearheaded by David Reiner) and the Manning lab at the Salk Institute.

Highlights

• Giardia lamblia strain WB has 278 protein kinases, but 198 of these belong to a huge expansion of the Nek family, most of which are catalytically active, and many of which are so divergent as to be at the borderline of detectability.
• The remaining 80 (the "core kinome") come from just 49 kinase classes found in other organisms, and a few small Giardia-specific families and unique kinases. This is the smallest core kinome of any organism known to survive in pure culture (i.e. omitting obligate parasites that have lost basic cellular functions and kinases.
• The core kinome is identical between the three Giardia strains (though the Neks are not). When we compare with the next closest (but still very distant) relative, Trichomonas vaginalis, and a more distant excavate, Leishmania major, we predict that early excavates had more core kinase classes, but lost them, maybe due to parasitism.

Resources

• Giardia lamblia on Wikipedia.
• GiardiaDB, the Giardia genome resource at EuPath, also hosts databases for Trichomonas and Leishmania.
• The genome papers for strains WB, GS and P15.