4-Coumarate CoA Ligase Family in Soybean Responds to Heterodera glycines

Soybean cyst nematode (SCN) development depends on syncytium formation, which requires cell-wall degradation and fusion. Lignin, the main barrier in cell walls, is critical for SCN resistance. 4-Coumarate: CoA ligase (4CL) drives the phenylpropanoid pathway by converting p-coumaric acid to p-coumaroyl-CoA, supplying lignin precursors. Here, resistant cv. Huipizhiheidou accumulated more lignin than susceptible Williams 82 after SCN inoculation. SCN stress induced distinct Gm4CL-family expression profiles across cultivars; Gm4CL3 and Gm4CL4 were markedly upregulated in Huipizhiheidou. Transient expression of Gm4CL3 in tobacco thickened leaf cell walls, implying enhanced wall reinforcement against SCN. Thus, 4CLs, especially Gm4CL3, may promote lignin deposition and secondary wall thickening to strengthen soybean SCN resistance.