From degradation to alleviation: Trichoderma facilitates plants resisting the PBAT stress through secreting a cutinase-like enzyme

The ecological impacts of biodegradable plastics like poly (butylene adipate-co-terephthalate) (PBAT) demand urgent investigation due to their unresolved risks to soil-plant systems, including physical interference with root development, disruption of indigenous microbial ecology. While PBAT depolymerization is a prerequisite for its removal, the slow and inefficient breakdown of these polymers in soil often results in the persistent accumulation of phytotoxic monomers, creating a bottleneck for biological remediation. In this study, through transcriptomic and phylogenetic analyses, we identified a key secreted hydrolase CUT2, belonging to a distinct clade of cutinase-like polyester hydrolases. Overexpression of cut2 (OEThcut2) significantly enhanced PBAT depolymerization, resulting in 27.0% and 22.4% increases in the release of terephthalic acid (TPA) and butanediolic acid (BTA) compared to the wild-type strain, respectively. The direct catalytic activity of purified CUT2 was confirmed through vitro film weight-loss assays with a degradation rate of 4.3% observed. In pot experiments, integrated multi-omics analysis revealed that the OEThcut2 strain reconfigured the rhizosphere microbial community and activated the aromatic degradation pathways, coinciding with the attenuated accumulation of degradation monomers. Furthermore, the enrichment of carbohydrate-active enzymes (CAZys) and the reduction of monomer burdens which revitalized the tricarboxylic acid cycle (TCA) and normalized redox homeostasis thereby clearing the metabolic bottleneck for intermediate turnover. Complementary monomer-exposure assays established that the reduction of PBAT monomers is critical for alleviating plant oxidative stress and growth inhibition. These findings provide a depolymerization to detoxification framework that links fungal enzymatic activity to rhizosphere metabolic recovery, offering a robust strategy for mitigating biodegradable plastic toxicity in agroecosystem.