Abstract text: Pectin is the most structurally diverse polysaccharide in the plant cell wall and requires coordinated action of numerous pectin-remodelling enzymes. Among these, polygalacturonases (PGs) play a central role in pectin depolymerisation. Structural analyses of Arabidopsis thaliana PGs revealed numerous cysteine residues forming disulphide bridges, suggesting potential redox regulation; however, the large number of PG isoforms complicates functional studies. Therefore, Marchantia polymorpha, with its reduced gene redundancy, was used as a model system. In this study, two PGs, MpPG2 and MpPG3, and a putative thiol reductase, MpGILT, were identified and studied. Recombinant proteins were heterologously expressed in Pichia pastoris and characterised in vitro. Microscale thermophoresis revealed binding affinities between MpGILT and both MpPGs, supporting direct interactions. These results were further validated in vivo by co-immunoprecipitation assays in Nicotiana benthamiana, which confirmed interactions between MpGILT and multiple MpPGs. Expression profiling showed overlapping expression patterns of MpGILT and MpPGs during thallus development. Moreover, phenotyping of MpGILT knock-out and overexpression lines demonstrated its crucial role in thallus growth. Collectively, these findings suggest that MpGILT may regulate PG activity through redox-dependent mechanisms, revealing a novel level of control in plant cell wall remodeling.