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Identifier

000336885

Title

Μοριακή και βιοχημική ανάλυση του γονιδίου AtPA02 που κωδικοποιεί για οξείδαση των πολυαμινών στην Arabidopsis thaliana

Alternative Title

Molecular and biochemical characterisation of AtPA02 g Gene that codes for a polyamine oxidase in Arabidopsis thaliana

Author

Ανδριοπούλου, Αθηνά

Thesis advisor

Ρουμπελάκη - Αγγελάκη, Καλλιόπη

Abstract

The plant PAOs that were first characterized catalyze the oxidative deamination of higher PAs (Spd, Spm) resulting to their terminal catabolism. In contrast, the mammalian cells exhibit a different catabolic process, in which PAs are back-converted to Put. Evidence for the existence of a similar catabolic pathway in plants was recently provided, through the characterization of the in vitro activity of AtPAO1 and AtPAO3, the two out of the five Α. thaliana PAOs. More specifically, in a recent study we showed that AtPAO3 gene encodes for a peroxisomal protein which is able to catalyze in vitro the sequential conversion/oxidation of Spm to Spd, and of Spd to Put, thus exhibiting a functional homology to the mammalian PAO. Aiming to further investigation of PA catabolism in A. thaliana, the role of AtPAO2 gene was studied. AtPAO2 along with AtPAO3 and AtPAO4 belong to the same paraphyletic group, while AtPAO2 shows an 84% homology with AtPAO3. The AtPAO2 cDNA was isolated and characterized and the corresponding protein was expressed and purified. Moreover, the protein’s in vitro activity and intracellular localization were identified. AtPAO2 does not oxidize Put, while it is able to catalyze the conversion of Spm to Spd and of Spd to Put, producing H₂O₂, similar to AtPAO3. Moreover, its action is significantly inhibited by guazatine, a potent PAO inhibitor. However, AtPAO2 was found to be localized to the chloroplasts and not to peroxisomes. Further investigation of the expression levels of AtPAO2 under stress conditions showed a differential gene regulation, compared to AtPAO3. For future study of the AtPAO2 function in vivo, homozygous mutants of A. thaliana col-0 were isolated. The overall data reinforce the view that a back- conversion pathway exists in plant polyamine catabolism and that the characterized plant proteins that participate in this pathway show both differential regulation and intracellular localization in A. thaliana.

Physical description

51 σ. : εικ. ; 30 εκ.

Language

Greek

Subject

Back-Conversion

PAO

Spermidine

Spermine

Αντίστροφος καταβολισμός

Σπερμίνη

Issue date