Second messengers involved in hypoxia signal transduction in Arabidopsis

ABSTRACT Due to flooding conditions or waterlogging, plants experience oxygen shortage (hypoxia or anoxia). In the context of climate change, plants are more likely to experience hypoxia do to the extremization of raining events. ‘Cell signaling’ is the way by which plants respond to environmental stimuli. As one of the most characterized signaling molecules, Ca2+ has been implicated in different responses shaping plant physiology, from wounding, to plant-microbe interaction, osmotic stress and so on. Ca2+ signaling also occur under oxygen shortage as revealed by both early and recent works in the field. During my Ph.D. project, I uncovered the role of an hypoxia-induced calcium-dependent kinase (CIPK25) in controlling plant adaptation to oxygen shortage (hypoxia and/or anoxia). To achieve this goal, I combined molecular biology techniques with interactomic and ionomic analysis to get insight into the effect of oxygen shortage on secondary signaling. Through the use of transgenic/mutant plants, gene expression analysis and fluorescence microscopy I characterized the physiological significance of CIPK25 induction under low-oxygen conditions. Using protein-protein interaction techniques, I discovered one of the targets of this protein, the AKT1 potassium channel, connecting the calcium-dependent signaling under anoxia to the regulation of potassium homeostasis. Concomitantly and aside to the main project, I started the development of new tools which will help in uncovering other targets of CIPK25 and the putative signaling role of K+ under environmental or endogenous low-oxygen conditions in the future. These include (I) transgenic plants for phospho-proteomic analysis, in order to discover different CIPK25 targets in time and space and (II) the exploitation of a genetically encoded K+ biosensor, which will help to decipher the signaling role of this ion in plants.