Lytic polysaccharide monooxygenase (LPMO) expression in Arabidopsis reduces cell wall recalcitrance and boosts immunity against Pseudomonas syringae.

Background Lytic Polysaccharide Monooxygenases (LPMOs) are well known for their ability to boost the efficiency of enzyme mixtures used for breaking down lignocellulosic biomass in vitro . Nonetheless, the impact of LPMO expression within plants and its influence on cell wall characteristics remains largely unexplored. Several studies have indicated that introducing cell wall degrading enzymes heterologously in plants can enhance saccharification efficiency. Hence, to understand the effects of LPMO expression in planta , we introduced the Auxiliary Activity (AA14) family gene from Pycnoporus coccineus ( PcAA14 ) into Arabidopsis thaliana . This was performed using a native signal peptide and was driven by both a constitutive ( 35S ) promoter and a xylem-specific ( Cinnamate-4-hydroxylase ) promoter. We then assessed how PcAA14 expression influenced plant growth, immune response, cell wall composition, and the efficiency of saccharification. Result PcAA14 was found to localise to the plasma membrane. Transgenic Arabidopsis lines expressing PcAA14 accumulated higher levels of oxidized xylo-oligosaccharides relative to wild-type plants after xylanase digestion which confirmed LPMO can be active in plants. Fourier Transform Infrared and mass spectroscopy analysis further revealed presence of oxidized polysaccharides in PcAA14 expressing plants. Furthermore, these transgenic plants exhibited increased cellulose content and reduced lignin content compared to wild-type. Cell walls from PcAA14 -expressing plants were more digested by Cellic CTec2 enzymatic cocktail and GH11 xylanase, indicating improved digestibility of major cell wall polysaccharides. Furthermore, expression of PcAA14 did not result in any observable morphological or anatomical abnormalities instead, these plants observed with improved immunity against Pseudomonas syringae. Conclusion Our study provides the first evidence that the heterologous expression of LPMO from PcAA14 in plants enhances the digestibility of cellulose and xylan, both with and without pretreatment. This approach holds promise for tailoring bioenergy crops to support the sustainable production of biobased products.