Differential regulation of wheat quinone reductases in response to powdery mildew infection.
ABSTRACT At least two types of quinone reductases are present in plants: (1) the zeta-crystallin-like quinone reductases (QR1, EC 18.104.22.168) that catalyze the univalent reduction of quinones to semiquinone radicals, and (2) the DT-diaphorase-like quinone reductases (QR2, EC 22.214.171.124) that catalyze the divalent reduction of quinones to hydroquinones. QR2s protect cells from oxidative stress by making the quinones available for conjugation, thereby releasing them from the superoxide-generating one electron redox cycling, catalyzed by QR1s. Two genes, putatively encoding a QR1 and a QR2, respectively, were isolated from an expressed sequence tag collection derived from the epidermis of a diploid wheat Triticum monococcum L. 24 h after inoculation with the powdery mildew fungus Blumeria graminis (DC) EO Speer f. sp. tritici Em. Marchal. Northern analysis and tissue-specific RT-PCR showed that TmQR1 was repressed while TmQR2 was induced in the epidermis during powdery mildew infection. Heterologous expression of TmQR2 in Escherichia coli confirmed that the gene encoded a functional, dicumarol-inhibitable QR2 that could use either NADH or NADPH as an electron donor. The localization of dicumarol-inhibitable QR2 activity around powdery mildew infection sites was accomplished using a histochemical technique, based on tetrazolium dye reduction.
- SourceAvailable from: Pradeepa Gunathilake Bandaranayake[Show abstract] [Hide abstract]
ABSTRACT: Parasitic plants in the Orobanchaceae develop haustoria in response to contact with host roots or chemical haustoria-inducing factors. Experiments in this manuscript test the hypothesis that quinolic-inducing factors activate haustorium development via a signal mechanism initiated by redox cycling between quinone and hydroquinone states. Two cDNAs were previously isolated from roots of the parasitic plant Triphysaria versicolor that encode distinct quinone oxidoreductases. QR1 encodes a single-electron reducing NADPH quinone oxidoreductase similar to zeta-crystallin. The QR2 enzyme catalyzes two electron reductions typical of xenobiotic detoxification. QR1 and QR2 transcripts are upregulated in a primary response to chemical-inducing factors, but only QR1 was upregulated in response to host roots. RNA interference technology was used to reduce QR1 and QR2 transcripts in Triphysaria roots that were evaluated for their ability to form haustoria. There was a significant decrease in haustorium development in roots silenced for QR1 but not in roots silenced for QR2. The infrequent QR1 transgenic roots that did develop haustoria had levels of QR1 similar to those of nontransgenic roots. These experiments implicate QR1 as one of the earliest genes on the haustorium signal transduction pathway, encoding a quinone oxidoreductase necessary for the redox bioactivation of haustorial inducing factors.The Plant Cell 04/2010; 22(4):1404-19. · 9.25 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: SUMMARY: To acquire iron from plant hosts, fungal pathogens have evolved at least two pathways for iron uptake. One system is hinged on the secretion and subsequent uptake of low-molecular-weight iron chelators termed siderophores, while the other uses cell-surface reductases to solubilize ferric iron by reducing it to ferrous iron for uptake. We identified five iron uptake-related genes from the head blight pathogen Fusarium graminearum and showed that they were transcribed in response to iron limitation. To examine the relative contribution of the reductive and siderophore pathways of iron uptake, we created mutants disrupted at the ferroxidase gene FET3 (Deltafet3) or the siderophore biosynthetic gene SID1 (Deltasid1). The Deltafet3 mutants produced wild-type amounts of siderophores and grew at the same rate as the wild-type under iron limitation, but accumulated high levels of free intracellular iron. The Deltasid1 mutants did not produce siderophores and grew slowly under low iron conditions. Transcription of the iron uptake-related genes was induced in the Deltasid1 mutant regardless of the growth medium iron content, whereas these genes were transcribed normally in the Deltafet3 mutant. Finally, the Deltasid1 mutants could infect single, inoculated spikelets, but were unable to spread from spikelet-to-spikelet through the rachises of wheat spikes, while the Deltafet3 mutants behaved as wild-type throughout infection. Together, our data suggest that siderophore-mediated iron uptake is the major pathway of cellular iron uptake and is required for full virulence in F. graminearum.Molecular Plant Pathology 07/2007; 8(4):411-21. · 3.88 Impact Factor
Article: Flavin-dependent quinone reductases.[Show abstract] [Hide abstract]
ABSTRACT: Quinones are abundant cyclic organic compounds present in the environment as well as in pro- and eukaryotic cells. Several species have been shown to possess enzymes that afford the two-electron reduction to the hydroquinone form in an attempt to avoid the generation of one-electron reduced semiquinone known to cause oxidative stress. These enzymes utilize a flavin cofactor, either FMN or FAD, to transfer a hydride from an electron donor, such as NAD(P)H, to a quinone substrate. This family of flavin-dependent quinone reductases shares a flavodoxin-like structure and reaction mechanism pointing towards a common evolutionary origin. Recent studies of their physiological functions in eukaryotes suggest a role beyond detoxication of quinones and involvement in the oxygen stress response. Accordingly, mammalian quinone reductases emerge as central molecular switches that control the lifespan of transcription factors, such as p53, and hence participate in the development of apoptosis and cell transformation.Cellular and Molecular Life Sciences CMLS 02/2008; 65(1):141-60. · 5.62 Impact Factor