The evolutionary transition of plants from aquatic to terrestrial environments resulted in adaptations to cope with various stresses and threats. Plant plasma membrane receptors, recognize extracellular signals and initiate immune and abiotic stress responses. MAP kinase (MPK) cascades transduce signals from such receptors by phosphorylating substrate proteins, which effectuate appropriate responses. By generating deletion lines of MPK genes in the simple, non-vascular moss Physcomitrella patens, I provide interesting evidence that MPKs may be important in the understanding of evolutionary changes of plant immunity required for the conquest of land by plants. I describe the role of MPKs (MPK3, MPK5, RAK1 & double knockout RAK1/RAK2) upon abiotic stress by characterizing the phenotypes and morphological changes there may be during stress treatments. I characterized the mutant phenotypes during treatment with phytohormones and osmotic and light stress.
This thesis contains of a general introduction to plant immunity and the role of MPKs in signaling processes related to immunity, abiotic stress, and plant development in both vascular and non-vascular plants. The focus in this thesis is on abiotic stress and development changes in the MPK mutants. Results are presented in the result part of the thesis, and in a draft manuscript summarizing data on novel rosetta proteins which combine a protein Nα-terminal acetyltransferase (NATD) and a MPK, here we called RAKs (Rosetta-Acetyltransferase-Kinase).
This thesis and work on these MPK mutants gives the laboratory a great start on several future publications, since many of the mutant lines have interesting phenotypes with and without exposure to abiotic stresses