Differences in the structure of plant polygalacturonases specify enzymes’ dynamics and processivities to fine-tune cell wall pectins

Abstract

The fine-tuning of pectins by polygalacturonases (PGs) plays a key role in modulating plant cell wall chemistry and mechanics, impacting plant development. The high number of plant PG isoforms and their absence of inhibition by endogenous PG-Inhibiting Proteins (PGIPs) question the regulation of pectin depolymerization during development. Our understanding of the diversity and of the regulation of plant PGs has been impaired by the lack of protein structures. Here we resolved the crystal structures of two PGs from Arabidopsis, PGLR and ADPG2, whose expression overlap in roots. By combining molecular dynamic simulations, analysis of enzymes kinetics and hydrolysis products we determined why plant PGs are not inhibited by PGIPs. We further showed that subtle differences in PGLR and ADPG2 structures translated into distinct dynamics and processivities, leading to peculiar effects on root development, as determined by exogenous applications of enzymes.

Cell adhesion maintenance and controlled separation in plants

“…We also pointed out several times the similarities in terms of enzymes involved in growth and cell separation associated cell wall remodeling, but it is important to note that these enzymes are part of large families and that their activities can vary and lead to radically different effects. It is for instance proposed that some endogenous PGs have an effect specifically for expansion and other more specifically for cell separation (Ogawa et al, 2009;Xiao et al, 2017;Safran et al, 2023). Furthermore, in the long term, sustained growth also involves additional cell wall synthesis and secretion, that would compensate for some of the cell wall loosening and adhesion weakening effect of cell wall remodeling enzymes.…”

TBL38 is an atypical homogalacturonan acetylesterase with a peculiar cell wall microdomain localization in Arabidopsis seed mucilage secretory cells

“…MSC surface wall powders were resuspended in 1 mL distilled water for 1 h. An aliquot (450 µL) was mixed with 50 µL of 500 mM sodium acetate buffer pH 5.0 and polysaccharides were hydrolyzed for 24 h at 40°C under 500 rpm shaking with either a pectin lyase (PL) specific for methylesterified HGs (Ralet et al, 2012), a polygalacturonase (PG) (Safran et al, 2023) specific for non-methylesterified HGs or a rhamnogalacturonase (RG, Swiss-Prot Q00018, provided by Novozymes, Copenhagen, Denmark) specific for the RGI backbone (Ralet et al, 2010).…”