The nonopisthokont septins: How many there are, how little we know about them, and how we might learn more.

We have confirmed and extended previous reports of a wide distribution of septin proteins in the eukaryotic phylogeny. It now appears that septins are present in at least some representatives of every eukaryotic supergroup, with the possible exception of the Excavata. Presently, almost nothing is known of the structure, assembly, and biological roles of septins outside of the opisthokonts (animals, fungi, and their close relatives). Thus, studies of the septins in the highly diverse and distantly related nonopisthokont groups present a major opportunity to gain a much deeper understanding of septin core function and evolution, and we discuss briefly the excellent prospects for capitalizing on this opportunity in the next few years.