Analysis of Spc98 homologues in the plant family Brassicaceae

Eukaryotic cells have a cytoskeleton, composed of flexible fibers that serve as support and transportation systems. One class of fibers is microtubules, which are hollow cylinders formed by tubulin dimers. Microtubules are organized in animal cells by a structure called the centrosome, which consists of two centrioles and a cloud of pericentriolar proteins. One of these proteins is gamma tubulin, which has been shown to nucleate microtubules. However, gamma‐ tubulin has recently been found to be part of a complex, called the gamma‐tubulin ring complex, which is composed of several proteins, including Spc98. The centrosome is not found in plants or fungi, and microtubule organizing centers are still being defined. One approach is to identify homologs to known centrosomal proteins. While gamma‐tubulin has been shown to be conserved in all eukaryotic organisms, homologs to components of the ring complex are still being delineated. The focus of this project is to identify homologs of Spc98 in plants, and to analyze their rate of evolutionary change. To this end we have begun with the plant family Brassicaceae, and are analyzing their genomes for Spc98 homologous proteins. A homolog has been identified in Arabidopsis, and is 45% similar to the human and yeast homologs in a conserved region [amino acids 319–809]. The rate of change in Spc98 homologs will be compared with that of gamma‐tubulin within the Brassicaceae.