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Abstract:
Sensing environmental factors and responding swiftly to them is essential for all living organisms. For instance, predators must act rapidly once prey is sensed. Nematode-trapping fungi (NTF) are predators that use "traps" differentiated from vegetative hyphae to capture, kill, and consume nematodes. These traps undergo drastic and rapid morphological changes upon nematode induction. Multiple signaling hubs have been shown to regulate this remarkable process. Here, we demonstrate that the conserved cAMP-PKA signaling pathway exerts a crucial role in trap morphogenesis of the nematode-trapping fungi Arthrobotrys oligospora. A gene deletion mutant of the PKA catalytic subunit TPK2 proved insensitive toward nematode presence. Moreover, we show that the G protein alpha subunit GPA2 acts upstream of adenylate cyclase, with GPA2 deletion resulting in substantially reduced trap formation, whereas exogenous provision of cAMP rescued the prey-sensing and trap morphogenesis defects of a gpa2 mutant. Thus, we show that cAMP production triggered by G protein signaling and downstream PKA activity are vital for prey-sensing and trap development in A. oligospora, demonstrating that this highly conserved signaling pathway is critical for nematode-trapping fungi and nematode predator-prey interactions.
