Activation and regulation of plasma membrane receptor signaling complexes controlling plant development and immunity, and their connection to downstream signaling cascades. – SICOPID

Double mutants phenotyping, in vitro pull down, co-immunoprecipitation, phosphoproteomics

Here, we identified that MAKR2 directly interacts with the receptor kinase TMK1 to regulate root gravitropism. We analyzed MAKR2 expression pattern, gain and loss of function phenotypes and interaction with TMK1. In particular, during the reporting period, we demonstrated the direct interaction between MAKR2 and TMK1 kinase domain using in vitro as well as in vivo experiments. We further showed that TMK1 phosphorylates MAKR2 likely to regulate its plasma membrane targeting in response to auxin.

We will now test the effect of TMK1-regulated phosphorylation on MAKR2 function, notably its subcellular localization and membrane interactions. We also worked on MAKR3, another member of the same family of RK inhibitor. We isolated gain and loss of function mutant but we haven’t found its cognate receptor yet, which will be our focus for the rest of the project.

We manuscript relating these findings is currently in revision

Plants are nature’s other successful experiment with multicellular life. To coordinate growth and development of their cells, tissues and organs plants have evolved unique plasma membrane receptor kinases (RKs). Several members of this protein family function as pattern recognition receptors, and as hormone receptors shaping the architecture of the plant. There is mounting evidence that different plant RKs are organized in membrane signaling complexes. RKs have a common structural architecture and share downstream signaling components. As such, it is presently unclear how the recognition of specific endogenous or foreign signals at the cell surface is translated into the activation of specific developmental programs or immune responses in the cytosol. We propose to combine physiology, genetics and cell biology with phosphoproteomics, quantitative biochemistry and structural biology to identify the shared and specific mechanisms by which plant developmental and immune receptor complexes are activated. We will dissect, in molecular detail, how activated receptor complexes generate specific signaling output in the cytosol and how the activity of plant RKs are regulated by inhibitor proteins. We envision that our work will provide a molecular framework for understanding how specificity is encoded at the molecular level in RK signaling, setting the stage for engineering these pathways in crops in the future.