Oxidation of pectin-derived oligogalacturonides balances the growth–defense trade-off by attenuating cell wall damage signaling
Moira Giovannoni (Italy)1; Valentina Scafati (Italy)1; Sara Di Renzo (Italy)2; Manuel Benedetti (Italy)1;
1 - Dept. of Life, Health and Environmental Sciences, University of L’Aquila, 67100 L’Aquila, Italy; 2 - Dept. of Biology and Biotechnologies 'Charles Darwin', Sapienza University of Rome, 00185 Rome, Italy;
Keywords: oligogalacturonides; redox regulation; growth-defense balance;
Abstract Topics: Theme 9: Cell Wall Function and Signaling in plant adaptation to Biotic and Abiotic Stresses
Type of Presentation: Oral Communication

Abstract text: Plant growth requires tight regulation of immune responses triggered by cell wall damage, yet the mechanisms limiting excessive immunity activation by cell wall-derived damage-associated molecular patterns (DAMPs) are not fully understood. Pectin hydrolysis mediated by fungal polygalacturonases (PGs) releases oligogalacturonides (OGs), a class of DAMPs that activate plant immune responses. To investigate redox-dependent regulation of pectin-derived OGs, we developed an inducible chimeric system in Arabidopsis thaliana combining a fungal polygalacturonase (FpPG), which generates OGs from pectin, with a plant oligogalacturonide oxidase (OGOX1), which catalyzes their oxidation. Expression of FpPG alone caused constitutive defense activation, leaf chlorosis, and severe growth inhibition. In contrast, coupling FpPG activity with OGOX1 attenuated defense responses and restored normal development. Consistently, co-infiltration of recombinant FpPG and OGOX1 in Nicotiana benthamiana showed that OGOX1 markedly reduced FpPG-induced reactive oxygen species production and callose deposition. This biochemical approach enabled the in vivo detection of oxidized OGs, which were associated with attenuated defense activation. Together, our findings demonstrate a functional coupling between PG and OGOX activities that operates as a redox-dependent switch controlling the growth–defense balance through OG generation and oxidation.

OGOX-mediated redox attenuation of PG-induced OG signaling balances plant growth and immunity: expression of FpPG alone caused constitutive defense activation and severe growth inhibition. Coupling FpPG activity with OGOX1 attenuated defense responses and restored normal development. Attenuation of defense responses is associated with the accumulation of oxidized OGs.