Ammonium Transporters Govern Nutrient Sensing and Trap Induction in the Nematode-Trapping Fungi Arthrobotrys oligospora

To survive nutrient scarcity, organisms must detect environmental cues and acquire essential resources efficiently. Under nutrient-limiting conditions, nematode-trapping fungi (NTF) such as Arthrobotrys oligospora form specialized traps to capture nematodes; this transition can be suppressed by the ready availability of carbon and nitrogen. Ammonium transporters of the MEP family are key regulators of nitrogen sensing and uptake across all forms of life. We identified three MEP genes in A. oligospora based on protein sequence homology. Functional assays revealed that loss of the MEP genes alters the fungus’s ability to produce traps, without affecting the morphology of the traps or their ability to function in catching nematodes. Heterologous expression in Saccharomyces cerevisiae revealed functional conservation of Mep transporter subclasses. Together, the Mep transporters of A. oligospora contribute to ammonium-regulated trap induction.