Functional Analysis of Peroxisomal Targeting Signal in Green Algae

Peroxisomes are ubiquitous organelles in eukaryotic cells. There are at least three types of peroxisomes in higher plant. Glyoxysomes contain some enzymes required for the beta -oxidation of fatty acids and the glyoxylate cycle in etiolated cotyledons. Leaf peroxisomes play a cucial role in photorespiration in combination with chloroplasts and mitochondria in green leaves. Unspesialized peroxisomes are in non-photosynthetic tissues. In Mougeotia and Spirogyra, enzymes of beta -oxidation were located in the peroxisomes. On the other hand, the peroxisomes from Eremosphaera and Chlorogonium did not contain enzymes of the glyoxylate cycle that are characteristic for glyoxysomes. Generally it appears that the peroxisomes isolated from unicellular algae are neither of the glyoxysomal nor of the leaf peroxisomal type. By searching database, we detected a similar parts of plant's peroxisomal targeting signal (PTS) in malate synthatase and malate dehydrogenase genes of Chlamydomonas reinhardtii. To know these enzymes are actually located in the peroxisomes and higher plant's PTS can act normally in unicellular green alga, we tried to express Green fluorescent protein fusion proteins with algal PTS or plant's PTS in Chlamydomonas and Chlosterium.