Recent Advances in Understanding the Roles of Pectin as an Active Participant in Plant Signaling Networks

Abstract

Pectin is an abundant cell wall polysaccharide with essential roles in various biological processes. The structural diversity of pectins, along with the numerous combinations of the enzymes responsible for pectin biosynthesis and modification, plays key roles in ensuring the specificity and plasticity of cell wall remodeling in different cell types and under different environmental conditions. This review focuses on recent progress in understanding various aspects of pectin, from its biosynthetic and modification processes to its biological roles in different cell types. In particular, we describe recent findings that cell wall modifications serve not only as final outputs of internally determined pathways, but also as key components of intercellular communication, with pectin as a major contributor to this process. The comprehensive view of the diverse roles of pectin presented here provides an important basis for understanding how cell wall-enclosed plant cells develop, differentiate, and interact.

Bimodally oriented cellulose fibers and reticulated homogalacturonan networks - A direct visualization of Allium cepa primary cell walls

“…Overall, our results regarding the nature and distribution of the meshing throughout the cell wall suggest that it consists of demethylesterified HGs. This fits well with the current understanding of pectin biosynthesis where pectins are synthesized in a methylated state in the Golgi Apparatus and demethylated in muro by endogenous methylesterases 24,41,42 and strongly interact with the cellulose fibers 39 , participating in the stifness of the primary cell wall 40 .…”

“…Overall, our results regarding the nature and distribution of the meshing throughout the cell wall suggest that it consists of demethylesterified HGs. This fits well with the current understanding of pectin biosynthesis where pectins are synthesized in a methylated state in the Golgi Apparatus and demethylated in muro by endogenous methylesterases 24,41,42 and strongly interact with the cellulose fibers 39 , participating in the stiffness of the primary cell wall 40 . The remnants observed in one instance (Figure 6B, E and F) could be more complex pectic polysaccharides such as rhamno-galacturonan-II, or the hemicellulosic component xyloglucan, shown to coat the cellulose fibers, possibly tethering them together as we observed in our tomograms (Figure 4C) 27 or HGs with a higher degree of methylation, and therefore little affected by the enzyme.…”

“…Pectins, mainly homogalacturonans (HGs), making up to 60% of the dry weight of the primary cell wall 4 , are hypothesized to surround all other components and act as a matrix 8 . Composition, methylation state, and calcium levels have been shown to change the mechanical properties of pectins by altering the level of crosslinking 23,24 .…”

Genomic Regions Associated with Fusarium Wilt Resistance in Flax

“…This enzyme degrades pectin, a major component of the plant cell wall. During infection, pathogens not only secrete pectin-degrading enzymes, but also hijack the host signalling pathways to induce cell remodelling by plant-derived enzymes [50].…”

Building an extensible cell wall

“…However, the physical state of pectin in native walls is not well defined because tools for characterizing higher-order pectic structures within complex walls are limited; the major tools include 13 C SS-NMR ( Foster et al, 1996 ; Ha et al, 1996 ; Wang et al, 2012 ; Temple et al, 2021 ), optical microscopy using fluorescent probes for pectins ( Rydahl et al, 2018 ; Voiniciuc et al, 2018b ) and scanning electron microscopy ( Domozych et al, 2014 ; Zhang et al, 2016 ). Current views on the potential roles of pectins in plant morphogenesis and growth are extraordinarily diverse and have been the subject of numerous reviews ( Palin and Geitmann, 2012 ; Saffer, 2018 ; Anderson and Kieber, 2020 ; Yang and Anderson, 2020 ; Haas et al, 2021 ; Shin et al, 2021 ). In this section, I summarize this complex and contradictory subject with regard to mechanisms of wall enlargement.…”