A novel temperature-sensitive immune pathway in plants

Abstract The immune system is crucial for plant survival, although its activation diverts resources away from other important processes, such as growth and reproduction. To balance the need for an effective immune response with the need to maintain overall fitness, plants have evolved immune priming. The priming or pre-activation of defence mechanisms allows plant cells to respond faster and more efficiently to an incoming threat without triggering the actual defence response. In this study, we reveal a novel molecular mechanism of temperature dependent immune priming mediated by the Arabidopsis extra-large GTP binding protein 2 (XLG2) contributing to resistance against pathogens such as Fusarium oxysporum and Pseudomonas syringae. We found that XLG2 rapidly accumulates in the nucleus upon temperature elevation and that nuclear localization is essential for XLG2-mediated defence responses. XLG2 directly interacts with several defence-related transcription factors and stabilizes transcription activation complexes, such as nonexpressor of pathogenesis related genes 1 (NPR1) and TGACG sequence-specific binding protein (TGA2). Our observations suggest that XLG2 integrates abiotic and biotic stress signals providing an important balance between immunity and fitness and thus enabling plants to adequately respond to a changing environment.