Biology subjects

Jorgensen, B.

Publications and source records attributed to Jorgensen, B..

5 recordsLinked to original sources

bioRxiv2025

Modulation of the GT Family 47 clade B gene affects arabinan deposition in elaters of Marchantia polymorpha

The plant cell wall polymer -1,5-linked arabinan is associated with important functions in plant physiology, such as cell wall flexibility and desiccation tolerance in angiosperms. However, its biosynthetic mechanism remains obscure. A putative arabinan arabinosyltransferase (AraT) is the Arabidopsis ARABINAN-DEFICIENT1 in GT family 47 clade B (GT47B), but its role is inferred by its mutant cell wall phenotypes, and not through in vitro assays. With seven other genes in the clade, investigating the function of the members in GT47B is hampered by the high genetic redundancy in Arabidopsis. Instead, we probe the function of the only two genes in GT47B in the liverwort model organism Marchantia polymorpha, named MpARAD-Like 1 (MpARADL1) and MpARADL2. Mparadl1 and Mparadl2 loss-of-function mutants and overexpression lines were generated, and their cell wall composition was probed using Comprehensive Microarray Polymer Profiling (CoMPP), glycosyl linkage analysis and immunolabelling. Interestingly, Mparadl2 mutants have much less of the 1,5--L-arabinan epitope in elaters since LM6 antibody recognition showed a notable reduction. However, 5-linked Araf levels in the Marchantia thallus tested with glycosyl linkage analysis are comparable between mutants and wild type, suggesting that there is another enzyme forming 5-Araf linkages in Marchantia. Our attempts to obtain the biochemical activity of these enzymes through the expression and purification of AtARAD1, MpARADL1 and MpARADL2 proteins in the HEK293 cell heterologous expression system were unsuccessful. Therefore, we suspect that an evolutionarily conserved, and clade-specific mechanism is required to confer solubility for purification and subsequent activity characterisation of GT47B proteins. Previous studies have shown that co-expression of protein interaction partners can enhance protein solubility in the HEK293 cell system, but co-expression of MpARADL2 with AtARAD1 and MpARADL1 did not yield soluble proteins, prompting further investigation into the protein-protein interactors of GT47B proteins.

plant biology↗

bioRxiv2022

Are cell wall traits a component of the succulent syndrome?

Succulence is an adaptation to low water availability characterised by the presence of water-storage tissues that alleviate water stress under low water availability. The succulent syndrome has evolved convergently in over 80 plant families and is associated with anatomical, physiological and biochemical traits. Despite the alleged importance of cell wall traits in drought responses, their significance in the succulent syndrome has long been overlooked. Here, by analysing published pressure-volume curves, we show that elastic adjustment, whereby plants change cell wall elasticity, is uniquely beneficial to succulents for avoiding turgor loss. In addition, we used comprehensive microarray polymer profiling (CoMPP) to assess the biochemical composition of cell walls in leaves. Across phylogenetically diverse species, we uncover several differences in cell wall biochemistry between succulent and non-succulent leaves, pointing to the existence of a succulent glycome. We also highlight the glycomic diversity among succulent plants, with some glycomic features being restricted to certain succulent lineages. In conclusion, we suggest that cell wall biomechanics and biochemistry should be considered among the characteristic traits that make up the succulent syndrome.

plant biology↗

bioRxiv2022

Cell wall extensin arabinosylation is required for root directional response to salinity

Soil salinity is a major contributor to crop yield losses. To improve our understanding of root responses to salinity, we developed and exploit here a real-time salt-induced tilting assay (SITA). This method follows root growth upon both gravitropic and salt challenges, revealing that root bending upon tilting is modulated by salinity, but not by osmotic stress. Next, this salt-specific response was measured in 345 natural Arabidopsis accessions and we discovered a genetic locus, encoding for the cell-wall modifying enzyme EXTENSIN ARABINOSE DEFICIENT TRANSFERASE (ExAD), to be associated with root bending in salt. Extensins are a class of structural cell wall glycoproteins [hydroxyproline-rich glycoproteins (HRGPs)] which are post-translationally modified by O-glycosylation mostly in the form of hydroxyproline (Hyp)-arabinosylation. We show that salt induces ExAD-dependent Hyp-arabinosylation, influencing root bending responses and cell wall thickness. We report that roots of exad mutants, which lack extensin Hyp-Araf4 modifications, display increased root epidermal cell wall thickness and porosity and altered gravitropic root bending in salt, as well as a reduced salt avoidance response. Our results suggest that extensin modification via Hyp-arabinosylation represents a novel salt-specific cellular process that is required for the directional response of roots exposed to salinity.

plant biology↗

bioRxiv2020

Golgi-localized exo-β1,3-galactosidases involved in AGP modification and root cell expansion in Arabidopsis

Plant arabinogalactan proteins (AGPs) are a diverse group of cell surface- and wall-associated glycoproteins. Functionally important AGP glycans are synthesized in the Golgi apparatus, but the relationships between their glycosylation, processing, and functionality are poorly understood. Here we report the identification and functional characterization of two Golgi-localized exo-{beta}-1,3-galactosidases from the glycosyl hydrolase 43 (GH43) family in Arabidopsis thaliana. GH43 loss of function mutants exhibit root cell expansion defects in sugar-containing growth media. This root phenotype is associated with an increase in the extent of AGP cell wall association, as demonstrated by Yariv phenylglycoside dye quantification and comprehensive microarray polymer profiling of sequentially extracted cell walls. Recombinant GH43 characterization showed that the exo-{beta}-1,3-galactosidase activity of GH43s is hindered by {beta}-1,6 branches on {beta}-1,3-galactans. In line with this steric hindrance, the recombinant GH43s did not release galactose from cell wall extracted glycoproteins or AGP rich gum arabic. These results show that Arabidopsis GH43s are involved in AGP glycan biosynthesis in the Golgi, and suggest their exo-{beta}-1,3-galactosidase activity influences AGP and cell wall matrix interactions, thereby adjusting cell wall extensibility.

plant biology↗

bioRxiv2018

The expa1-1 mutant reveals a new biophysical lateral root organogenesis checkpoint

In plants, post-embryonic formation of new organs helps shape the adult organism. This requires the tight regulation of when and where a new organ is formed, and a coordination of the underlying cell divisions. To build a root system, new lateral roots are continuously developing, and this process requires asymmetric cell division in adjacent pericycle cells. Characterization of an expansin a1 (expa1) mutant has revealed a novel checkpoint during lateral root formation. Specifically, a minimal pericycle width was found to be necessary and sufficient to trigger asymmetric pericycle cell divisions during auxin-driven lateral root formation. We conclude that a localized radial expansion of adjacent pericycle cells is required to position the asymmetric cell divisions and generate a core of small daughter cells, which is a prerequisite for lateral root organogenesis.\n\nSIGNFICANCE STATEMENTOrgan formation is an essential process in plants and animals, driven by cell division and cell identity establishment. Root branching, where lateral roots form along the primary root axis, increases the root system and aids capture of water and nutrients. We have discovered that tight control of cell width is necessary to co-ordinate asymmetric cell divisions in cells that give rise to a new lateral root organ. While biomechanical processes have been shown to play a role in plant organogenesis, including lateral root formation, our data give new mechanistic insights into the cell size checkpoint during lateral root initiation.

plant biology↗