Gene Deletion of 7,8-Linoleate Diol Synthase of the Rice Blast Fungus:Studies on pathogenicity, stereochemistry and oxygenation mechanisms

Jernerén, Fredrik, Sesma, Ane, Francheschetti, Marina, Hamberg, Mats and Oliw, Ernst 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: 21 May 2020 00:16
URI: https://ueaeprints.uea.ac.uk/id/eprint/73344
DOI: 10.1074/jbc.M109.062810

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