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 126.96.36.199) that catalyze the univalent reduction of quinones to semiquinone radicals, and (2) the DT-diaphorase-like quinone reductases (QR2, EC 188.8.131.52) 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: library2.usask.ca
- [Show abstract] [Hide abstract]
ABSTRACT: Plants respond to low temperatures through an intricately coordinated transcription network which results in cold acclimation, a phenomenon by which plants increase their freezing tolerance. To analyse the global transcriptome of Eucalyptus gunnii cold-acclimated leaves, 2,662 ESTs were classified by FunCat and the corresponding transcripts quantified throughout a cold acclimation programme using macro-array technique. This combined analysis resulted in the description of the temporal patterns of gene expression with regard to their identity and corresponding functional categories. This paper proposes a predictive hierarchical classification of the main protective mechanisms likely to participate in the increased cold tolerance of E. gunnii. Given the time course and level of the LEA/dehydrin accumulation, the cryoprotection through proteins may explain most of the hardening. This cryoprotection would be completed by sugar synthesis (raffinose and maltose). As a permanent response, red-ox regulation and protection of membranes or macromolecules against peroxidation look mainly associated with metallothioneins. A limited part of cold response seems to be dedicated to dehydration avoidance through osmoprotectants or to frost avoidance through antifreeze proteins and deposition of cuticle wax.Trees 01/2013; 27(6). · 1.87 Impact Factor