Biology subjects

Augustin, S.

Publications and source records attributed to Augustin, S..

3 recordsLinked to original sources

bioRxiv2018

Crystal structures of two tandem malectin-like receptor kinases involved in plant reproduction

A complex cell-to-cell communication between the male pollen tube and the female reproductive organs is required for plant fertilization. A family of Catharanthus roseus Receptor Kinase-1 ( CrRLK1L) membrane receptors has been genetically implicated in this process. Here we present crystal structures of the CrRLK1Ls ANXUR1 and 2 at 1.48 and 1.1 [A] resolution, respectively. Our structures reveal a novel arrangement of two malectin-like domains connected by a short {beta}hairpin linker and stabilized by calcium ions. The canonical carbohydrate interaction surfaces of related animal and bacterial carbohydrate binding modules are not conserved among plant CrRLK1Ls. In line with this, we failed to detect binding of chemically diverse oligosaccharides to ANXUR1 and HERCULES1. Instead, CrRLK1Ls have evolved a protein-protein interface between their malectin domains, which forms a deep cleft lined by highly conserved aromatic and polar residues. Analysis of the glycosylation pattern of different CrRLK1Ls and their oligomeric states together suggests that this cleft could resemble a binding site for a ligand required for CrRLK1Ls receptor activation.

plant biology↗

bioRxiv2018

Integration of Brassinosteroid and Phytosulfokine Signalling Controls Vascular Cell Fate in the Arabidopsis Root

Multicellularity arose independently in plants and animals, but invariably requires robust determination and maintenance of cell fate. This is exemplified by the highly specialized water-and nutrient-conducting cells of the plant vasculature, which are specified long before their commitment to terminal differentiation. Here, we show that the hormone receptor BRASSINOSTEROID INSENSITIVE 1 (BRI1) is required for root vascular cell fate maintenance, as BRI1 mutants show ectopic xylem in procambial position. However, this phenotype is unrelated to classical brassinosteroid signalling outputs. Instead, BRI1 is required for the expression and function of its interaction partner RECEPTOR-LIKE PROTEIN 44 (RLP44), which, in turn, associates with the receptor for the peptide hormone phytosulfokine (PSK). We show that PSK signalling is required for the maintenance of procambial cell identity and is quantitatively controlled by RLP44, which promotes complex formation between the receptor for PSK and its co-receptor. Mimicking the loss of RLP44, PSK-related mutants show ectopic xylem in the position of procambium, whereas rlp44 can be rescued by exogenous PSK. Based on these findings, we propose that RLP44 controls cell fate by connecting BRI1 and PSK signalling, providing a mechanistic framework for the integration of signalling mediated by the plethora of plant receptor-like kinases at the plasma membrane.

plant biology↗

bioRxiv2018

A Comprehensive Tool Set for Inducible, Cell Type-Specific Gene Expression in Arabidopsis

Understanding the context-specific role of gene function is a key objective of modern biology. To this end, we generated a resource for inducible cell-type specific trans-activation based on the well-established combination of the chimeric GR-LhG4 transcription factor and the synthetic pOp promoter. Harnessing the flexibility of the GreenGate cloning system, we produced a comprehensive set of GR-LhG4 driver lines targeting most tissues in the Arabidopsis shoot and root with a strong focus on the indeterminate meristems. We show that, when combined with effectors under control of the pOp promoter, tight temporal and spatial control of gene expression is achieved. In particular, inducible expression in F1 plants obtained from crosses of driver and effector lines allows rapid assessment of the cell type-specific impact of an effector with high temporal resolution. Thus, our comprehensive and flexible toolbox is suited to overcome the limitations of ubiquitous genetic approaches, the outputs of which are often difficult to interpret due to widespread existence of compensatory mechanisms and the integration of diverging effects in different cell types.\n\nOne sentence summary: A set of lines enabling spatio-temporal control of gene expression in Arabidopsis.

plant biology↗