Arabidopsis BNT1, an atypical TIR-NBS-LRR gene, acting as a regulator of the hormonal response to stress.

During their life cycle, plants have to cope with fluctuating environmental conditions. The perception of the stressful environmental conditions induces a specific stress hormone signature specifying a proper response with an efficient fitness. By reverse genetics, we isolated and characterized a novel mutation in Arabidopsis, associated with environmental stress responses, that affects the At5g11250/BURNOUT1 (BNT1) gene which encode a Toll/Interleukin1 receptor-nucleotide binding site leucine-rich repeat (TIR-NBS-LRR) protein. The knock-out bnt1 mutants displayed, in the absence of stress conditions, a multitude of growth and development defects, suchas severe dwarfism, early senescence and flower sterility, similar to those observed in vitro in wild type plants upon different biotic and/or abiotic stresses. The disruption of BNT1 causes also a drastic increase of the jasmonic, salicylic and abscisic acids as well as ethylene levels. Which was consistent with the expression pattern observed in bnt1 showing an over representation of genes involved in the hormonal response to stress? Therefore, a defect in BNT1 forced the plant to engage in an exhausting general stress response, which produced frail, weakened and poorly adapted plants expressing "burnout" syndromes. Furthermore, by in vitro phenocopying experiments, physiological, chemical and molecular analyses, we propose that BNT1 could represent a molecular link between stress perception and specific hormonal signature.