Biology subjects

Temple, H.

Publications and source records attributed to Temple, H..

3 recordsLinked to original sources

bioRxiv2022

Eudicot primary cell wall glucomannan is related in synthesis, structure and function to xyloglucan

The functional differences between plant cell wall hemicelluloses such as glucomannan, xylan and xyloglucan (XyG) remain unclear. These polysaccharides influence assembly and properties of the wall, perhaps by interacting with cellulose to affect the deposition and bundling of the fibrils. As the most abundant hemicellulose, XyG is considered important in eudicot primary cell walls (PCWs), but plants devoid of XyG show relatively mild phenotypes. We report here that a patterned {beta}-galactoglucomannan ({beta}-GGM) is widespread in PCW of eudicots and shows remarkable similarities to XyG. The sugar linkages forming the backbone and side chains of {beta}-GGM are analogous to those that make up XyG, and moreover, these linkages are formed by glycosyltransferases from the same CAZy families. Solid-state NMR indicated that {beta}-GGM shows low mobility in the cell wall, consistent with interaction with cellulose. Although Arabidopsis {beta}-GGM synthesis mutants show no obvious growth defects, genetic crosses between {beta}-GGM and XyG mutants produce exacerbated phenotypes compared to XyG mutants. These findings demonstrate a related role of these two similar but distinct classes of hemicelluloses in PCWs. This work will provide new avenues to study the roles of both {beta}-GGM and XyG in PCWs. One sentence summaryPatterned {beta}-GGM resembles xyloglucan in structure, biosynthesis and function.

plant biology↗

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↗

bioRxiv2021

Two softwood GUX clades are responsible for distinct glucuronic acid patterns on xylan.

Wood of coniferous (softwood) trees, is a globally significant carbon sink and an important source of biomass for industrial applications. Despite its importance, very little is known about the genetic basis of softwood biosynthesis. Glucomannan and xylan are the main hemicelluloses in softwood secondary cell walls. Xylan interacts with the cellulose fibrils in a two-fold screw configuration. Moreover, we have shown that xylan GUX (GlucUronic acid substitution of Xylan)-dependent branching with glucuronic acid is critical for biomass recalcitrance. Here, we investigated the decoration patterns of xylan by softwood GUX enzymes. Using in vitro and in planta assays we demonstrate that two distinct clades of conifer GUX enzymes are active glucuronyltransferases. Interestingly, these enzymes have different specific activities, with one adding evenly spaced GlcA branches and the other one being also capable of glucuronidating two consecutive xyloses. Since xylan patterning might modulate xylan-cellulose and xylan-lignin interactions, our result further the understanding of softwood biosynthesis and can contribute to strategies aimed at modifying softwood cell wall properties.

plant biology↗