Sweet immunity and disease resistance in tobacco and rice.

Plants are often exposed to various stresses. Both stress hormones and small sugars function as “stress” signals during adaptive responses. Although the idea of sugar-enhanced defense responses (“sweet immunity” or “sweet priming”) was launched more than half a century ago, little effort has been undertaken to understand the underlying mechanisms, that are probably linked to the “damaged self” hypothesis, predicting that increased levels of endogenous sugars in the plant cell wall (cellular leakage) trigger defense responses. First, sweet priming will be attempted by exogenous application of an array of sugars at different doses to boost the innate immunity of rice and tobacco. Primed plants will be challenged by different types of hemibiotrophic and necrotrophic pathogens and disease resistance will be evaluated. Second, endogenous sugar and hormone levels will be evaluated in mutant lines affected in sugar signaling and sugar metabolism, in the absence and presence of pathogens. Primed and non-primed wild-type and mutant plants will be investigated at the whole plant level, including phloem sap analyses and systemic effects. The specific role of cell wall invertases in sweet immunity will be investigated. Third and timepermitting, developmental and diurnal aspects will be considered. This approach may lead to the development of cheap alternatives for toxic agrochemicals for a sustainable agriculture.