The pH-dependent processivity of Arabidopsis AtPME2 can control cell wall mechanical properties

Pectin methylesterases (PMEs) modify homogalacturonan’s chemistry and thereby play a key role in regulating primary cell wall mechanical properties. How PME activity can fine-tune pectin structure in the growing plant has remained elusive, in part due to the lack of available biochemically-characterized enzymes to empirically test functional properties. Here we report on AtPME2, which we found to be highly expressed during lateral root emergence as well as root and hypocotyl elongation. Production of mature active enzyme in Pichia pastoris allowed its biochemical characterization. We show that AtPME2 can switch from full processivity (at pH 8), creating large blocks of unmethylated galacturonic acid, to low processivity (at pH 5) and relate these observations to the differences in electrostatic potential of the protein. We also produced a generic plant PME antiserum suitable for detecting recombinant and native enzyme independent of species source. In the context of acidified apoplast, we showed using reverse genetics that low-processive demethylesterification by AtPME2 can loosen the cell wall, with consequent increase in cell elongation and etiolated hypocotyl length. Our study brings insights into how the pH-dependent regulation by PME activity could affect pectin structure and associated cell wall mechanical properties in expansion.

The potential of pectin to impact pig nutrition and health: feeding the animal and its microbiome

ABSTRACT The increasing efforts to substitute antibiotics and improve animal health combined with the acknowledgement of the role of gut microbiota in health have led to an elevated interest in the understanding on how fibre with prebiotic potential, such as pectin, can improve animal growth and health via direct or gut microbiota mediated effects. Various reports exist on the antiviral and antibacterial effects of pectin, as well as its potency as a modulator of the immune response and gut microbial community. Comprehensive insights into the potential of pectin to improve animal growth and health are currently still hampered by heterogeneity in the design of studies. Studies differ with regard to the dosage, molecular structure and source of the pectin implemented, as well as concerning the set of investigations of its effects on the host. Harmonisation of the study design including an in-depth analysis of the gut microbial community and its metabolome will aid to extract information on how pectin can impact growth and overall animal health. Studies with an increased focus on pectin structure such as on pectin-derived rhamnogalacturonan I (RG-I) are just starting to unravel pectin-structure-related effects on mammalian health.

Pectin structure and particle size modify carotenoid bioaccessibility and uptake by Caco-2 cells in citrus juices vs. concentrates

Pectin changes from a citrus-based product modify bioaccessibility and carotenoid uptake by intestinal cells.