At least two types of quinone reductases are present in plants: (1) the zeta-crystallin-like quinone reductases (QR1, EC 184.108.40.206) that catalyze the univalent reduction of quinones to semiquinone radicals, and (2) the DT-diaphorase-like quinone reductases (QR2, EC 220.127.116.11) 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.
"A pathogen, such as P. syringae, might profit from a delayed onset of cell death during the biotrophic phase of its life cycle, a situation that mimics the response of QR KO mutants in this study. In contrast another biotroph, the powdery mildew Blumeria graminis, induced a QR gene in wheat (Greenshields et al. 2005). In this latter case, the upregulation was thought to increase the ability of the attacked cells to remove quinones under conditions where the normal antioxidant system is overtaxed. "
[Show abstract][Hide abstract] ABSTRACT: Quinone reductases (EC 18.104.22.168) are flavoproteins that protect organisms from oxidative stress. The function of plant quinone reductases has not as yet been addressed in vivo despite biochemical evidence for their involvement in redox reactions. Here, using knock-out and over-expressing lines, we studied the protective role of two groups of Arabidopsis thaliana cytosolic quinone reductases, Nqr and Fqr, in response to infection by necrotrophic fungi. The knock-out lines nqr- and fqr1- displayed significantly slower development of lesions of Botrytis cinerea and Sclerotinia sclerotium in comparison to the WT. Consistent with this observation, the over-expressing line FQR1+ was hypersensitive to the pathogens. Both the nqr- and fqr1- displayed increased fluorescence of 2',7'-dichlorofluorescein, a reporter for reactive oxygen species in response to B. cinerea. Infection by B. cinerea was accompanied with increased Nqr and Fqr1 protein levels in the WT as revealed by western blotting. In addition, a marked stimulation of salicylic acid-sensitive transcripts and supression of jasmonate-sensitive transcripts was observed in moderately wounded QR KO mutant leaves, a condition mimicking the early stage of infection. In contrast to the above observations, germination of conidia was accelerated on leaves of QR KO mutants in comparison with the WT and FQR1+ . The same effect was observed in water-soluble leaf surface extracts. It is proposed that the altered interaction between B. cinerea and the quinone reductase mutants is a consequence of subtly altered redox state of the host, which perturbs host gene expression in response to environmental stress such as fungal growth.
Physiologia Plantarum 03/2013; 149(3). DOI:10.1111/ppl.12042 · 3.14 Impact Factor
Available from: Pradeepa Gunathilake Bandaranayake
"n a primary response to exposure to benzoquinones and naphtho - quinones ( Matvienko et al . , 2001b ) . Transcription of xenobiotic metabolizing enzymes is often regulated by their substrates and has been observed in plants , animals , and fungi ( Prestera and Talalay , 1995 ; Testa , 1995 ; Akileswaran et al . , 1999 ; Laskowski et al . , 2002 ; Greenshields et al . , 2005 ) . DT - diaphorase ( menadi - one reductase activity ) is induced in mammalian cells treated with a wide range of electrophilic chemical carcinogens ( Cadenas et al . , 1992 ) . Xenobiotic responsive elements ) upstream of the rat quinone reductase gene have been identified that are responsible for its transcriptional activation by exo"
[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. DOI:10.1105/tpc.110.074831 · 9.34 Impact Factor
"RNA and DNA were isolated as previously described (Greenshields et al., 2005). DNA and RNA gel blots on GeneScreen Plus membranes (PerkinElmer, Wellesley, MA) were prepared as described by Sambrook and Russell (2001). "
[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.
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