Poster: Organelle Biogenesis

Abs # 1149: Investigation of Nobel Plant Peroxisomal Functions by Monitoring Gene Expression Profiles

Presenter:	Tomoe, Kamada , kamada@nibb.ac.jp
Authors	Tomoe, Kamada  (A) (B)  Makoto, Hayashi  (B)   Mikio, Nishimura  (A) (B)
Affiliations:	(A): The Graduate University for Advanced Studies (B): National Institute for Basic Biology

In higher plants, peroxisomes are subdivided functionally into glyoxysomes, leaf peroxisomes and unspecialized peroxisomes. The glyoxysomes are present in cells of storage organs, such as cotyledons during post-germinative growth of oil-seed plants. It contains enzymes for fatty acid b-oxidation and the glyoxylate cycle, and plays a pivotal role in the conversion of lipid into sucrose. In contrast, leaf peroxisomes are found widely in cells of photosynthetic organs. It has been shown that some of the enzymes responsible for photorespiration are localized in leaf peroxisomes. Other organs, such as roots, contain unspecialized peroxisomes whose function is still obscure. We have previously demonstrated that peroxisomal proteins contain one of two targeting signals, namely PTS1 and PTS2. Determination of Arabidopsis whole genome allowed us to identify candidates of genes that encode proteins containing either PTS1 or PTS2. To understand functional differentiation of plant peroxisomes, we extensively surveyed expression profile of these genes in various organs. Cluster analysis of the data revealed that these genes could be classified into 5 groups, namely class A-E. Class A genes expressed exclusively in roots. Most of class A genes has not been functionally identified. In contrast, class B genes expressed exclusively in seedling. All known genes encoding enzymes for b-oxidation and glyoxylate cycle were classified in this class. Class C genes expressed abundantly in green cotyledons and rosette leaves. It contained genes encoding enzymes necessary for photorespiratory glycolate metabolism. Upon these data, we re-examine functional classification of plant peroxisomes.