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

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 and determined why plant PGs are not inhibited by PGIPs. By combining molecular dynamic simulations, analysis of enzymes’ kinetics and hydrolysis products, we showed that subtle differences in PGLR and ADPG2 structures translated into distinct dynamics and processivities. This leads to peculiar effects on root development, as determined by exogenous applications of enzymes