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 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.
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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; DOI:10.1111/ppl.12042 · 3.26 Impact Factor
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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 · 9.58 Impact Factor
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ABSTRACT: When Manduca sexta attacks Nicotiana attenuata, fatty acid-amino acid conjugates (FACs) in the larvae's oral secretions (OS) are introduced into feeding wounds. These FACs trigger a transcriptional response that is similar to the response induced by insect damage. Using two-dimensional gel electrophoresis, matrix-assisted laser desorption ionization-time of flight, and liquid chromatography-tandem mass spectrometry, we characterized the proteins in phenolic extracts and in a nuclear fraction of leaves elicited by larval attack, and/or in leaves wounded and treated with OS, FAC-free OS, and synthetic FACs. Phenolic extracts yielded approximately 600 protein spots, many of which were altered by elicitation, whereas nuclear protein fractions yielded approximately 100 spots, most of which were unchanged by elicitation. Reproducible elicitor-induced changes in 90 spots were characterized. In general, proteins that increased were involved in primary metabolism, defense, and transcriptional and translational regulation; those that decreased were involved in photosynthesis. Like the transcriptional defense responses, proteomic changes were strongly elicited by the FACs in OS. A semiquantitative reverse transcription-PCR approach based on peptide sequences was used to compare transcript and protein accumulation patterns for 17 candidate proteins. In six cases the patterns of elicited transcript accumulation were consistent with those of elicited protein accumulation. Functional analysis of one of the identified proteins involved in photosynthesis, RuBPCase activase, was accomplished by virus-induced gene silencing. Plants with decreased levels of RuBPCase activase protein had reduced photosynthetic rates and RuBPCase activity, and less biomass, responses consistent with those of herbivore-attacked plants. We conclude that the response of the plant's proteome to herbivore elicitation is complex, and integrated transcriptome-proteome-metabolome analysis is required to fully understand this ubiquitous ecological interaction.Plant physiology 01/2007; 142(4):1621-41. DOI:10.1104/pp.106.088781 · 7.39 Impact Factor