Giardia Bares All: Parasite genes reveal long sexual history. Research done by surveying genome data.

Science News Online, Jan. 29, 2005 reports:

A new research finding provides evidence that sexual reproduction started as soon as life forms that have nuclei and organelles within their cells branched off from their structurally simpler ancestors.

The parasite Giardia intestinalis is well known for causing a diarrheal disease that animals and people contract after drinking contaminated water. Many researchers consider this species to be one of the most ancient living members of the eukaryote, or true nucleus, lineage. However, unlike most eukaryotes, G. intestinalis and its relatives have been long considered to reproduce only asexually — by division into two identical cells.

To determine when reproduction via sperm and eggs originated, John Logsdon of the University of Iowa in Iowa City and his colleagues took a close look at G. intestinalis' mysterious reproductive life. …

[Logsdon found that] G. intestinalis possesses genes similar to those used for meiosis by other eukaryotes. At least 5 of those genes function only in meiosis, and 10 others have roles both in meiosis and other functions, Logsdon's team noted in the Jan. 26 Current Biology.

Presumably this is significant biologically since it seems to establish a very early date for sexual reproduction. It also raises some questions. From the same article.

All living eukaryotes, including G. intestinalis, share numerous cellular features and processes that aren't seen in prokaryotes. According to Andrew Roger of Dalhousie University in Halifax, Nova Scotia, establishing that all eukaryotes are capable of meiosis could "make the evolutionary transition from prokaryote to eukaryote even more difficult to sort out.

"A lot had to happen when eukaryotes evolved. Why aren't there any intermediate stages of this process alive today? Did all the intermediate forms go extinct, and why?" Roger asks.

Logsdon says that he and his team plan to continue their research by looking for meiosis genes in other eukaryotes thought to be asexual.

Besides the biology, what I find interesting is the method of research. Here is an extract from the abstract of the original article: ScienceDirect - Current Biology : A Phylogenomic Inventory of Meiotic Genes: Evidence for Sex in Giardia and an Early Eukaryotic Origin of Meiosis.

We surveyed the ongoing G. intestinalis genome project data [7] and have identified, verified, and analyzed a core set of putative meiotic genes — including five meiosis-specific genes — that are widely present among sexual eukaryotes. The presence of these genes indicates that: (1) Giardia is capable of meiosis and, thus, sexual reproduction, (2) the evolution of meiosis occurred early in eukaryotic evolution, and (3) the conserved meiotic machinery comprises a large set of genes that encode a variety of component proteins, including those involved in meiotic recombination.

In other words, the reseach was done by looking at data archived as part of various genome projects. Presumably this is on-line information available to anyone. You just have to know what you are looking for.

This is a nice example of one of the benefits of digitizing and indexing the world as I mentioned in an earlier post.