Carbohydrate metabolism in plant-pathogen interactions. Regulation of the primary metabolism in plant-pathogen interactions
The interaction of pathogens and plants is accompanied by a profound reorganization of the metabolic status of host cells. Pathogen infected tissues are characterized by a progressively reduction in photosynthetic rates at the site of pathogen attack (Scholes et al., 1994, New Phytol. 126: 213–222) and an increased sink strength mediate by elevated invertase and hexose transporter expression. This was explicitly shown for the interaction of powdery mildew in barley and Arabidopsis (Fotopolous et al., 2003, Plant Physiol. 132: 821-829; Swarbrick et al., 2006, Plant Cell Environ. 29: 1061–1076). Thereby, increased hexose levels may function to supply energy for defence reactions (Biemelt and Sonnewald, 2006, J. Plant Physiol. 163: 307-318; Roitsch et al., 2003, J. Exp. Bot. 54: 513-524).
Our research focuses on the reorganization of the primary energy metabolism during biotic stress adaptation in Arabidopsis and barley. Thus, we genetically interfere with corresponding metabolic enzymes and analyze the performance of photosynthesis, the activity of key metabolic enzymes, gene expression, and defence responses in course of the interaction with pathogens of different trophic lifestyles.
In particular, we are interested in the function of alcoholic fermentation in course of plant-pathogen interactions. Besides the well-described role of alcohol dehydrogenase (ADH) in the flooding response and in seed and pollen metabolism (Strommer, 2011, The Plant Journal 66: 128-142) there is increasing evidence for a function of the fermentative pathway in biotic interactions. Recently we could establish a role of two barley ADHs, HvADH1 and HvADH2, in the interaction with the powdery mildew Blumeria graminis f.sp. hordei (Pathuri et al., 2011, J. Exp. Bot. 62: 3449-3457; Proels et al., 2011, Plant Signal. Behav. 6: 1548-1587). Additionally, we found an involvement of ADH1 in the systemic induced resistance of barley to B. graminis f.sp. hordei (Käsbauer et al. 2018). The site of pathogen attack is characterized by a reduction in photosynthetic rates, stomata closure and formation of reactive oxygen species, conditions which in all probability result in reduced oxygen pressure. Under those conditions ADH may have a function in keeping upright the glycolytic/fermentative pathway and thereby maintaining energy metabolism or channeling carbon units between sugar and lipid metabolisms. However, the mechanisms regulating this ADH-mediated metabolic reprogramming are not understood despite its critical function in the biotic stress response. Our aim is to find new molecular mechanisms in metabolic regulation in course of plant-pathogen interactions. Results could provide means to ensure crop yield under changing environmental conditions.