Biology subjects

Amsbury, S.

Publications and source records attributed to Amsbury, S..

3 recordsLinked to original sources

bioRxiv2024

Structurally diverse calloses/β-1,3-glucans in plant cell wall microdomains

Cell walls underpin the mechanics of cell growth, intercellular signalling, and defence against pathogenic organisms. {beta}-(1,3)-glucans (also known as callose) are polysaccharides found in plants, fungi, and some bacterial species. In developing plant organs, callose accumulates around intercellular channels (plasmodesmata) controlling cell-to-cell communication. We developed monoclonal antibodies for the detection of {beta}-(1,3)-glucans and using these identified distinct populations of callose differing in size and secondary structure. Callose sub-populations were in proximal but not overlapping cell wall microdomains implying distinct spatial and functional microenvironments. We also unveiled callose interaction with xyloglucan; another plant glycan regulating cell wall functions. This work challenges previous views demonstrating structural heterogeneity in plant callose and supporting interactions between glycans with roles in the regulation of cell wall properties and functions.

plant biology↗

bioRxiv2024

Hybrid xyloglucan utilisation loci are prevalent among plant-associated Bacteroidota

The plant hemicellulose xyloglucan (XyG) is secreted from the roots of numerous plant species, including cereals, and contributes towards soil aggregate formation in terrestrial systems. Whether XyG represents a key nutrient for plant-associated bacteria is unclear. The phylum Bacteroidota are abundant in the plant microbiome and provide several beneficial functions for their host. However, the metabolic and genomic traits underpinning their success remain poorly understood. Here, using proteomics, bacterial genetics, and genomics, we revealed that plant-associated Flavobacterium, a genus within the Bacteroidota, can efficiently utilise XyG through the occurrence of a distinct and conserved gene cluster, referred to as the Xyloglucan Utilisation Loci (XyGUL). Flavobacterium XyGUL is a hybrid of the molecular machinery found in gut Bacteroides spp., Cellvibrio japonicus, and the plant pathogen Xanthomonas. Combining protein biochemistry, computational modelling and phylogenetics, we identified a mutation in the enzyme required for initiating hydrolysis of the XyG polysaccharide, an outer membrane endoxyloglucanase glycoside hydrolase family 5 subfamily 4 (GH5_4), which enhances activity towards XyG. A subclade of GH5_4 homologs carrying this mutation were the dominant form found in soil and plant metagenomes due to their occurrence in Bacteroidota and Proteobacteria. However, only in members of the Bacteroidota spp., particularly Flavobacterium spp. was such a remarkable degree of XyGUL conservation detected. We propose this mechanism enables plant-associated Flavobacterium to specialise in competitive acquisition of XyG exudates and that this hemicellulose may represent an important nutrient source, enabling them to thrive in the plant microbiome, which is typified by intense competition for low molecular weight carbon exudates.

microbiology↗

bioRxiv2021

Comparative meta-proteomic analysis for the identification of novel plasmodesmata proteins and regulatory cues.

A major route for cell-to-cell signaling is via cell wall-embedded pores termed plasmodesmata (PD) forming the symplasm. PD regulate many aspects of plant development and responses to the environment however, our understanding of what factors affect their structure and permeability is limited. In this paper, a meta-analysis is presented as a tool for the identification of conditions affecting PD transport and in silico generation of PD proteomes for species of interest. The custom-built pipeline searches the whole genome for protein structural features and conserved domains identified on experimental proteomes and use it to predict PD candidates in 22 compatible plant species. Using the in silico proteome and microarray analysis, interactions between PD genes and conditions affecting PD function are identified. High salinity and osmotic stress affect a significant number of PD candidate genes and we provide evidence that these conditions regulate symplasmic transport of GFP. Using the pipeline, the in silico PD proteome for Medicago truncatula was generated, as an example of a plant in which experimental data is not available. The identification of a candidate receptor like protein was experimentally validated in M. truncatula transgenic roots expressing fluorescently tagged protein fusion. Together the results highlight the power of our newly designed tool in the identification of new factors and proteins influencing PD in diverse plant species.

plant biology↗