Biology subjects

Echevarria-Poza, A.

Publications and source records attributed to Echevarria-Poza, A..

4 recordsLinked to original sources

bioRxiv2024

Glucomannan engineering highlights the role of galactosyl modification in fine-tuning cellulose-glucomannan interaction in Arabidopsis cell walls

Widely found in most plant lineages, {beta}-mannans are structurally diverse polysaccharides that can bind to cellulose fibrils to form the complex polysaccharide architecture of the cell wall. Glucomannan backbones acquire variable patterns of galactosyl substitutions, depending on plant developmental stage and species. How the changes in polysaccharide structure influence its cell wall solubility or promote appropriate interaction with cellulose fibrils is poorly understood. Here, we show that fine-tuning of galactosyl modification on glucomannans is achieved by the differing acceptor recognition of mannan -galactosyltransferases (MAGTs). Biochemical analysis and 13C solid-state nuclear magnetic resonance spectroscopy of Arabidopsis with cell wall glucomannan engineered by MAGTs revealed that the degree of galactosylation strongly affects the interaction with cellulose. The findings indicate that plants tailor galactosyl modification on glucomannans for constructing an appropriate cell wall architecture, paving the way to convert properties of lignocellulosic biomass for better use.

bioengineering↗

bioRxiv2024

Convergent Acquisition of Glucomannan β-galactosyltransferases in Asterids and Rosids

{beta}-Galactoglucomannan ({beta}-GGM) is a primary cell wall polysaccharide in rosids and asterids. The {beta}-GGM polymer has a backbone of repeating glucose and mannose, usually with mono- or di-galactosyl sidechains on the mannosyl residues. CELLULOSE SYNTHASE-LIKE 2 (CSLA2), MANNAN -GALACTOSYLTRANSFERASE (MAGT), and MANNAN {beta}-GALACTOSYLTRANSFERASE (MBGT) are required for {beta}-GGM synthesis in Arabidopsis thaliana. The single MBGT identified so far, AtMBGT1, lies in glycosyltransferase family 47A subclade VII, and was identified in Arabidopsis. However, despite the presence of {beta}-GGM, an orthologous gene is absent in tomato (Solanum lycopersicum), a model asterid. In this study, we screened candidate MBGT genes from the tomato genome, functionally tested the activities of encoded proteins, and identified the tomato MBGT (SlMBGT1) in GT47A-III. Interestingly therefore, AtMBGT1 and SlMBGT1 are located in different GT47A subclades. Further, phylogenetic and glucomannan structural analysis from different species raised the possibility that various asterids possess conserved MBGTs in GT47A-III, indicating that MBGT activity has been acquired convergently among asterids and rosids. Although functional convergence was observed, the acquired amino acid substitutions among the two MBGT groups were not shared, suggesting different evolutionary pathways to achieve the same biochemical outcome. The present study highlights the promiscuous emergence of donor and acceptor preference in GT47A enzymes, and suggests an adaptive advantage for eudicots to acquire {beta}-GGM {beta}-galactosylation.

plant biology↗

bioRxiv2023

Differing structures of galactoglucomannan in eudicots and non-eudicot angiosperms

The structures of cell wall mannan hemicelluloses have changed during plant evolution. Recently, a new structure called {beta}-galactoglucomannan ({beta}-GGM) was discovered in eudicot plants. This galactoglucomannan has {beta}-(1,2)-Gal--(1,6)-Gal disaccharide branches on some mannosyl residues of the strictly alternating Glc-Man backbone. Studies in Arabidopsis revealed {beta}-GGM is related in structure, biosynthesis and function to xyloglucan. However, when and how plants acquired {beta}-GGM remains elusive. Here, we studied mannan structures in many sister groups of eudicots. All glucomannan structures were distinct from {beta}-GGM. In addition, we searched for candidate mannan {beta}-galactosyltransferases (MBGT) in non-eudicot angiosperms. Candidate AtMBGT1 orthologues from rice and Amborella did not show MBGT activity in vivo. However, the AtMBGT1 orthologue from rice showed MUR3-like xyloglucan galactosyltransferase activity in complementation analysis using Arabidopsis. Further, reverse genetic analysis revealed that the enzyme contributes to proper root growth in rice. Together, gene duplication and diversification of GT47A-VII in eudicot evolution may have been involved in the acquisition of mannan {beta}-galactosyltransferase activity. Our results indicate that {beta}-GGM is likely to be a eudicot-specific mannan.

biochemistry↗

bioRxiv2021

Discovery of putative Golgi S-Adenosyl methionine transporters reveals the importance of plant cell wall polysaccharide methylation

Polysaccharide methylation, especially that of pectin, is a common and important feature of land plant cell walls. Polysaccharide methylation takes place in the Golgi apparatus and therefore relies on the import of S-adenosyl methionine (SAM) from the cytosol into the Golgi. However, to date, no Golgi SAM transporter has been identified in plants. In this work, we studied major facilitator superfamily members in Arabidopsis that we identified as putative Golgi SAM transporters (GoSAMTs). Knock-out of the two most highly expressed GoSAMTs led to a strong reduction in Golgi-synthesised polysaccharide methylation. Furthermore, solid-state NMR experiments revealed that reduced methylation changed cell wall polysaccharide conformations, interactions and mobilities. Notably, the NMR revealed the existence of pectin egg-box structures in intact cell walls, and showed that their formation is enhanced by reduced methyl-esterification. These changes in wall architecture were linked to substantial growth and developmental phenotypes. In particular, anisotropic growth was strongly impaired in the double mutant. The identification of putative transporters that import SAM into the Golgi lumen in plants provides new insights into the paramount importance of polysaccharide methylation for plant cell wall structure and function.

plant biology↗