Pectin Demethylesterification Generates Platforms that Anchor Peroxidases to Remodel Plant Cell Wall Domains

Abstract

Highlights d Remodeling of plant cell wall domains necessitates wallpolarized molecular scaffolds d PMEI6 creates a partially demethylesterified pectin platform in a cell wall domain d PRX36 is anchored to this pectin platform during early seed development d PRX36 loosens the wall domain during late seed development for dry seed functions

Seed mucilage evolution: Diverse molecular mechanisms generate versatile ecological functions for particular environments

“…This organized explosion is carefully prepared earlier during MSC seed development by differential cell wall polysaccharide deposition and localized modifications. The polysaccharidicproteinaceous molecular scaffold enabling the A. thaliana primary wall domain loosening starts to be uncovered (Francoz et al, 2019;Kunieda et al, 2013;Saez-Aguayo et al, 2013). In flax, the MSC polysaccharide composition and its internal organization are proposed to play a role in proper MSC opening (Miart et al, 2019).…”

“…For this reason, in the following part, we will shed light on molecular mechanisms underlying this morphological diversity through intra-species and inter-species comparative studies for seed mucilage evolution understanding. (Francoz et al, 2019;Western, 2001), and in the emerging model L. usitatissimum on the right (Adapted from reference Miart et al (2019).). The 30-50 μm wide cells from both species are drawn to similar scale, the released mucilage layers are not drawn to scale.…”

“…and PRX36 encode enzymes necessary for proper seed mucilage hydration and extrusion (Dean et al, 2007;Kunieda et al, 2013;Saez-Aguayo et al, 2013) and PMEI6 and PRX36 functions are tightly and sequentially related (Francoz et al, 2019). As non-myxospermous seeds have a much better buoyancy efficiency and considering that the habitat of Sha is close to a river, seed dispersal by water run-off is one of the seed mucilage functions proposed to explain the loss of myxospermy (Macquet, Ralet, Loudet, et al, 2007;Saez-Aguayo et al, 2014).…”

Laccases and Peroxidases Co-Localize in Lignified Secondary Cell Walls throughout Stem Development

“…For example, a protein scaffold containing AtPRX64, AtCASP1, and the NADPH oxidase AtRbohF is required for localized lignin polymerization in the Casparian strip of Arabidopsis roots(Lee et al, 2013). Another PRX, AtPRX36, was also shown to bind to specific motifs of demethylesterified pectin in primary cell walls of seed coats, providing a "platform" for restricted PRX activity in a given location(Francoz et al, 2019).It is therefore possible that different lignin-associated LACs and PRXs have specific binding domains within SCWs or cell corners, although this has not been studied in stem tissues. Alternatively, mobility in the cell wall may impact localization, as proteins could diffuse to different regions of the cell wall following secretion.…”

Plant Cell Wall Proteins and Development

“…Each member has its own regulatory pathway during development or upon stress, and even if the proteins of a give family share the same functional domains, subtle differences can confer different biological activities. As an example, AtPrx36 plays a particular role in mucilage release because of the timely regulation of expression of its gene during seed development, and of its anchoring in a cell wall microdomain [37]. Most cell wall protein families are conserved in the green lineage.…”