Abstract.
The fungus Arthrobotrys dactyloides produces specialized constricting rings to trap and then consume nematodes. The signal transduction pathway involved in the nematode-trapping process was examined. Mastoparan, an activator of G-protein, had a stimulatory effect on the inflation of ring cells, whereas a G-protein inhibitor, pertussis toxin, prevented ring-cell expansion. The 40-kDa Gα of heterotrimeric G-proteins was specifically ADP-ribosylated by pertussis toxin. Using an antibody specific to the 35-kDa subunit Gβ, we showed that immunogold-labeled Gβ was more concentrated in ring cells than in the hyphae. In the absence of nematodes, the rings could be inflated by either pressurizing the culture in a syringe, raising intracellular Ca2+ concentrations, or adding warm water. We used these methods to reveal differences in responses to antagonists. The results support a model in which the pressure exerted by a nematode on the ring activates G-proteins in the ring cells. The activation leads to an increase in cytoplasmic Ca2+, activation of calmodulin, and finally the opening of water channels. The ring cells expand to constrict the ring and thus immobilize the nematode.
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Received: 13 April 2000 / Accepted: 22 June 2000
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Chen, TH., Hsu, CS., Tsai, PJ. et al. Heterotrimeric G-protein and signal transduction in the nematode-trapping fungus Arthrobotrys dactyloides . Planta 212, 858–863 (2001). https://doi.org/10.1007/s004250000451
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DOI: https://doi.org/10.1007/s004250000451