The pectate lyase FlPL1 fine-tunes jasmonate/auxin homeostasis to maintain symbiotic colonization by the endophytic fungus Fusarium lateritium

While pectate lyases are crucial for pathogen colonization via pectin degradation, their roles in endophytic fungi remain largely unexplored. This study characterizes FlPL1, a pectate lyase from the endophyte Fusarium lateritium. FlPL1 was highly expressed during Nicotiana benthamiana colonization and exhibited confirmed pectin-degrading activity. Deleting FlPL1 did not affect hyphal growth but impaired pectin utilization, decreased colonization efficiency, and diminished the fungus’s plant growth-promoting effects. Furthermore, FlPL1 loss intensified host immune responses by upregulating the jasmonic acid (JA) pathway (increasing JA-Ile and Me-JA) while reducing auxin (IAA and IBA) levels, triggering an antagonistic JA-auxin interplay. Additionally, FlPL1 alone could independently induce a JA-dependent host immune response. Ultimately, FlPL1 facilitates F. lateritium colonization and promotes plant growth by degrading pectin and modulating host hormone balances to suppress immunity. This study unveils the novel dual regulatory function of an endophyte-derived pectate lyase, providing new insights into endophytic colonization mechanisms.