Gene Deletion of 7,8-Linoleate Diol Synthase of the Rice Blast Fungus STUDIES ON PATHOGENICITY, STEREOCHEMISTRY, AND OXYGENATION MECHANISMS

Jerneren, F., Sesma, A., Francheschetti, M., Hamberg, M. and Oliw, E. H. (2010) Gene Deletion of 7,8-Linoleate Diol Synthase of the Rice Blast Fungus STUDIES ON PATHOGENICITY, STEREOCHEMISTRY, AND OXYGENATION MECHANISMS. Journal of Biological Chemistry, 285. pp. 5308-5316. ISSN 0021-9258

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Abstract

Linoleate diol synthases (LDS) are heme enzymes, which oxygenate 18:2n-6 sequentially to (8R)-hydroperoxylinoleic acid ((8R)-HPODE) and to (5S,8R)-dihydroxy-, (7S,8S)-dihydroxy-, or (8R,11S)-dihydroxylinoleic acids (DiHODE). The genome of the rice blast fungus, Magnaporthe oryzae, contains two genes with homology to LDS. M. oryzae oxidized 18:2n-6 to (8R)-HPODE and to (7S,8S)-DiHODE, (6S,8R)-DiHODE, and (8R,11S)-HODE. Small amounts of 10-hydroxy-(8E,12Z)-octadecadienoic acid and traces of 5,8-DiHODE were also detected by liquid chromatography-mass spectrometry. The contribution of the 7,8-LDS gene to M. oryzae pathogenicity was evaluated by replacement of the catalytic domain with hygromycin and green fluorescent protein variant (SGFP) cassettes. This genetically modified strain Δ7,8-LDS infected rice leaves and roots and formed appressoria and conidia as the native fungus. The Δ7,8-LDS mutant had lost the capacity to biosynthesize all the metabolites except small amounts of 8-hydroxylinoleic acid. Studies with stereospecifically deuterated linoleic acids showed that (8R)-HPODE was formed by abstraction of the pro-S hydrogen at C-8 and antarafacial oxygenation, whereas (7S,8S)-DiHODE and (8R,11S)-DiHODE were formed from (8R)-HPODE by suprafacial hydrogen abstraction and oxygenation at C-7 and C-11, respectively. A mac1 suppressor mutant (Δmac1 sum1–99) of M. oryzae, which shows cAMP-independent protein kinase A activity, oxygenated 18:2n-6 to increased amounts of (10R)-HPODE and (5S,8R)-DiHODE. Expression of the 7,8-LDS gene but not of the second homologue was detected in the suppressor mutant. This suggests that PKA-mediated signaling pathway regulates the dioxygenase and hydroperoxide isomerase activities of M. oryzae.

Item Type: Article
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: LivePure Connector
Date Deposited: 11 Dec 2019 02:33
Last Modified: 11 Dec 2019 02:33
URI: https://ueaeprints.uea.ac.uk/id/eprint/73344
DOI: 10.1074/jbc.M109.062810

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