TOLs, modulators during abiotic stress responses

Climate change and its impact on the adaptive capacity of plants is a highly topical area of research. Plants, as sessile organisms, cannot simply move away from an unfavorable environment and have therefore evolved intricate mechanisms to rapidly and precisely respond and adapt to their environment. This project addresses the cellular response of higher plants to drought stress, which is coordinated by the hormone abscisic acid (ABA). To modulate and fine-tune the ABA signaling pathway, key proteins are down-regulated by degradation. We intend to functionally characterize the involvement of the TOL (TOM1-like) protein family in the degradation of these key components, as a tol mutant plant line is more drought resistant than a wild-type plant line of the same ecotype it resembles under standard conditions. TOL proteins initiate the transport of plasma membrane-associated proteins, which are marked for degradation by ubiquitination, to the vacuole. Thus, in this project, a strong focus is placed on E3 ligases that catalyze the transfer of the protein ubiquitin to another protein. In addition, to link the function of TOL genes to the regulation of ABA responses, the genetic interaction of TOLs with ABA biosynthesis and signaling mutants will be investigated. Furthermore, subunits of the transport complex involved in ABA receptor degradation will be examined for interaction with TOLs to reveal functional linkages. ABA transporters and receptors as well as TOL reporter lines will be investigated with respect to their localization and abundance in different tol mutant backgrounds under drought stress. Thus, this project will elucidate how TOL proteins function in modulating the ABA pathway in plants. In summary, this project will contribute to the understanding of how TOLs, in addition to their general role in the endosomal degradation pathway, play a more differentiated role in the ABA signaling pathway that regulates drought stress. Fine-tuning of signaling pathways allows plants to adapt to their environment to respond resilliently to a changing environment.