Designing strategies to uncover MAPK specific functions in plant development

Abstract

As sessile organism, plants have acquired strategies to adjust their growth and development toenvironmental fluctuations. This flexibility relies on mechanisms to perceive and integrate conflicting signals. In eukaryotes, mitogen-activated protein kinases (MAPKs) are well known integrators of developmental and stress signals.Traditional genetic approaches, however, have two major obstacles when trying to uncover how MAPK signaling works: 1) redundancy obscures MAPK functions, so combinatorial mutants need to be generated, often resulting in pleiotropic effects; 2) some MAPKs are promiscuous and shared between different signaling cascades (yet signal-to-output specificity is guaranteed). To uncover the cellular logic behind MAPK cascades and their specificity-enforcing mechanisms, we usethe developmentofstomata (theepidermalvalves that regulate gas exchange), a process controlled by MAPK signaling. Here, we present a genetic screen looking forsuppressorsof a severestomatalclustering phenotype caused by the artificial activation of the MAPK cascade. Among five suppressors, we found a known MAPK with novel rolesin latestomatal development. This finding not only validates our screen, but also provides a context to study specificity-enforcing mechanisms. Our preliminary results suggest that activity level and subcellular localization mightcontribute to signaling specificity.