Poster: Organelle Biogenesis
Abs #
1141: Cellular responses under defects in glyoxysomal function duing post-germinative growth
|
|
Presenter: |
Hayashi, Makoto , makoto@nibb.ac.jp |
Authors | Hayashi, Makoto (A) Mikio, Nishimura (A) | | Affiliations: |
(A): National Institute for Basic Biology
|
|
|
Peroxisomes in higher plant cells are known to differentiate into at least three different classes, namely glyoxysomes, leaf peroxisomes and unspecialized peroxisomes. Each organelle contains a unique set of enzymes that provides special functions in various organs in higher plants. Glyoxysomes are present in cells of storage organs, such as endosperms and cotyledons during post-germinative growth of oil-seed plants, as well as in senescent organs. They contain enzymes for fatty acid b-oxidation and the glyoxylate cycle, and play a pivotal role in the conversion of seed-reserved lipids into sucrose. The seed-reserved lipids are deposited in lipid bodies as triacylglycerols. The fatty acids produced from the triacylglycerols are thought to be exclusively degraded in glyoxysomes during germination and post-germinative growth.
We have isolated Arabidopsis mutants that had defects in fatty acid b-oxidation by using 2,4-dichlorophenoxybutyric acid. Of those, we succeeded in identifying three alleles, PED1, PED2 and PED3. PED1 encodes 3-ketoacyl CoA thiolase, an enzyme that catalyzes the final step of fatty acid b-oxidation. PED3 gene encodes peroxisomal membrane "full-size" ABC transporter, that may transport fatty acids into glyoxysomes. In contrast, PED2 gene product, AtPex14p, is indirectly involved in fatty acid b-oxidation by regulating peroxisomal protein targeting. All three mutants have reduced activity for lipid degradation. Therefore, these mutants require exogenous supply of sucrose for germination.
These mutants give us an unique experimental system to understand cellular responses during germination. As an initial attempt, we compare gene expression of the mutants. We will discuss function of genes that alter their expression in the mutants.
