Periodic Reporting for period 4 - DIRNDL (Directions in Development)
Reporting period: 2024-03-01 to 2025-05-31
Most cells are organised in space. To function properly, cells often have distinct domains exposed to for example the outer and inner surfaces. This organization in space is referred to as cell polarity, and is a widespread property across kingdoms. In multicellular organisms, polarity domains are often aligned with organismal (front/back, outer/inner, left/right, etc) axes. Furthermore, important decisions, such as the orientation of cell division, are coupled to cell polarity. As such, cell polarity is a fundamental principle connected to normal development and disease. While cell polarity has been studied in substantial detail in single-celled yeasts and in animal models, knowledge is much more limited in the plant kingdom. From genomic analyses, it appears that plants, yeasts and animals do not share proteins in cell polarity pathways, and therefore it is largely unknown whether there are common or distinct molecular mechanisms that drive cell polarisation.
The DIRNDL project builds on recent findings by the principal investigator's team that 1) established the tools for using the early plant embryo as a model system for genetically investigating the establishment of cell polarity in the plant kingdom; 2) offer a set of novel polarity proteins in plants that allow for a proteomics strategy to map the polar proteome and 3) identified a deep protein homology of a shared structural domain that mediates protein polarity across animal and plant kingdoms. The DIRNDL project takes an integrated approach to genetically, proteomically and mechanistically dissect cell polarisation in plants (Arabidopsis and Marchantia).
The DIRNDL project builds on recent findings by the principal investigator's team that 1) established the tools for using the early plant embryo as a model system for genetically investigating the establishment of cell polarity in the plant kingdom; 2) offer a set of novel polarity proteins in plants that allow for a proteomics strategy to map the polar proteome and 3) identified a deep protein homology of a shared structural domain that mediates protein polarity across animal and plant kingdoms. The DIRNDL project takes an integrated approach to genetically, proteomically and mechanistically dissect cell polarisation in plants (Arabidopsis and Marchantia).
The project has been successful in achieving its main goals:
1. Through cross-kingdom analysis, detailed molecular characterization, and mutant analysis, we could show that the plant SOSEKI proteins are functionally analogous to animal cell polarity proteins. We also identified a minimal mechanism for polar membrane localization, and found that SOSEKI proteins are indispensable for cell division in both haploid and diploid cells and across land plants.
2. By using proteomic strategies, we discovered a set of conserved, polar proteins across land plants. This also enabled the identification of polarized enzymes that catalyze polar membrane association of other proteins.
3. Through genetic screening, we identified several genes in Arabidopsis that are required for viability and for cell polarity in the embryo. At the same time, we discovered that cell polarity extends to the haploid gametophyte stage, and this has significant consequences for the strategies to identify polarity regulators. Inspired by this result, we have started to screen for polarity factors in the haploid phase.
4. We have employed minimal systems to understand the requirements for cell polarity, and found a major polarity-organizing activity for SOSEKI proteins.
Most of these results will be published in journal papers soon, following the completion of the DIRNDL project.
1. Through cross-kingdom analysis, detailed molecular characterization, and mutant analysis, we could show that the plant SOSEKI proteins are functionally analogous to animal cell polarity proteins. We also identified a minimal mechanism for polar membrane localization, and found that SOSEKI proteins are indispensable for cell division in both haploid and diploid cells and across land plants.
2. By using proteomic strategies, we discovered a set of conserved, polar proteins across land plants. This also enabled the identification of polarized enzymes that catalyze polar membrane association of other proteins.
3. Through genetic screening, we identified several genes in Arabidopsis that are required for viability and for cell polarity in the embryo. At the same time, we discovered that cell polarity extends to the haploid gametophyte stage, and this has significant consequences for the strategies to identify polarity regulators. Inspired by this result, we have started to screen for polarity factors in the haploid phase.
4. We have employed minimal systems to understand the requirements for cell polarity, and found a major polarity-organizing activity for SOSEKI proteins.
Most of these results will be published in journal papers soon, following the completion of the DIRNDL project.