Knockout of SsArl1 Leading to Enhanced Virulence in Sclerotinia sclerotiorum

Sclerotinia sclerotiorum is a formidable soilborne fungus that wreaks havoc on numerous crops globally. While the role of ADP-ribosylation factor-like 1 (Arl1) small GTPases in vesicular trafficking and fungal development is well-documented, their specific impact on S. sclerotiorum remains unclear. Through reverse genetic techniques, we identified and characterized SsArl1, a typical Arl small GTPase conserved across fungi. Deleting SsArl1 hampers the hyphal growth of S. sclerotiorum, but leads to higher oxalic acid buildup and boosts cellulase activity. This speeds up the infection of host plants, yet increases their sensitivity to certain environmental stresses, particularly ionic and cell wall-related stress. Our results reveal that SsArl1 acts as a negative regulator of oxalic acid accumulation and virulence, while playing a positive role in enhancing resistance to environmental stresses in S. sclerotiorum.