Abiotic stress signalling in extremophile land plants

Plant life relies on complex arrays of environmental stress sensing and signalling mechanisms. Extremophile plants develop and grow in harsh environments with extremes of cold, heat, drought, desiccation or salinity, which have resulted in original adaptations. In accordance with their polyphyletic origins, extremophile plants likely possess core mechanisms of plant abiotic stress signalling. However, novel properties or regulations may have emerged in the context of extremophile adaptations. Comparative omics of extremophile genetic models, like Arabidopsis lyrata, Craterostigma plantagineum, Eutrema salsugineum, Physcomitrella patens, reveal diverse strategies of sensing and signalling that lead to general improvement of abiotic stress responses. Current research points out to putative differences of sensing and emphasises significant modifications of regulatory mechanisms, at the level of secondary messengers (Ca2+, phospholipids, reactive oxygen species), signal transduction (intracellular sensors, protein-kinases, transcription factors, ubiquitin-mediated proteolysis) or signalling crosstalk. Involvement of hormone signalling, especially ABA signalling, cell homeostasis surveillance and epigenetics mechanisms also shows that large-scale gene regulation, whole-plant integration, and probably stress memory are important features of adaptation to extreme conditions. This evolutionary and functional plasticity of signalling systems in extremophile plants may have important implications for plant biotechnology, crop improvement and ecological risk assessment under conditions of climate change.

Keywords: abscisic acid; calcium signalling; epigenetics; halophyte; phospholipid signalling; programmed cell death; reactive oxygen species signalling; retrograde signalling.