Die Kernregulatoren der Zellwand-Integrität bei Landpflanzen
Zusammenfassung der Projektergebnisse
In plant cells, cell wall integrity (CWI) mechanisms that monitor the performance of the extracellular cell wall to coordinate with the intracellular activities are governed by a complex and robust interplay between the transmembrane malectin-like receptors (MLRs), their secreted peptide ligands of the Rapid Alkalinisation Factor (RALF) family and downstream effectors such as the receptor-like cytoplasmic kinase MARIS (MRI) of the PTI1-like family. In the flowering plant model Arabidopsis thaliana, the MLRs AtFERONIA (AtFER) and its closest homologues AtANXUR1/2 (AtANX1/2) function upstream of AtMRI to orchestrate the CWI pathways of the tip-growing root hairs and pollen tubes, respectively. As such, genetic disruption of AtFER leads to root hairs that burst precociously during growth while the simultaneous disruption of both AtANX1 and AtANX2 triggers pollen tube bursting. Interestingly, loss of AtMRI recapitulate both tip-growing cell bursting phenotypes. Nonetheless, these CWI pathways remain particularly hard to decipher due to complex, sometimes partial, functional redundancy between the multigene family members of regulators. Earlier, we had demonstrated that CWI of the tip-growing rhizoids in the early diverging land plant Marchantia polymorpha, requires functional MpFER and MpMRI, both unique representatives of the MLR and PTI1-like families in Marchantia. This indicated that a genetic program for maintaining CWI was established early during land plant evolution and adopted later by higher plants for root hair and pollen tube growth control. The main objective of this proposal is to identify and characterize the interacting partners of the conserved MpFER/MpMRI signaling module and its upstream and downstream components in the control of CWI mechanisms by exploiting and developing further the liverwort Marchantia polymorpha system. Due to my permanent move to the Institute Sophia Agrobiotech, France and the Interaction Plant-Oomycete team, and consequently the early termination of this funding, only a couple of approaches were initiated. First, we started the construction of a Marchantia cDNA library for a Gateway-compatible yeast-two-hybrid approach followed by Next-Generation Sequencing. A first checkpoint analysis indicated we obtained approx. 4 x 106 clones of which 6-8 x 105 are full-length clones covering 45% of the Marchantia genome. We now aim to screen this new library for interactors of MpFER and MpMRI. Second, we performed a comparative transcriptomic and proteomic analyses of Mpfer and Mpmri mutants. Our results show an enrichment for abscisic acid (ABA) and defense response-related gene/peptides families among the differentially expressed/abundant transcripts/peptides common to our CWI mutants. Whether our CWI mutants exhibit altered responses to ABA and infection with the oomycete Phytophthora palmivora is currently under investigation.
