Responses to transient receptor potential (TRP) channel agonists in Chlamydomonas reinhardtii

Pungent substances, such as capsaicin and gingerol, activate the transient receptor potential (TRP)-V1 channel and affect the feeding behaviors of animals. To gain insight into how living organisms have acquired a sense for pungent substances, we explored the response to TRP agonists in a protist, Chlamydomonas reinhardtii. When capsaicin or gingerol was applied to wild-type cells, they became immotile, with flagella detaching from the cell body. The degree of deflagellation was nearly halved in a mutant defective in the TRP channel ADF1. Deflagellation in the adf1 mutant was inhibited further by Ruthenium Red, indicating ADF1 and another TRP channel are involved in the deflagellation response. The response to capsaicin and gingerol was not inhibited by TRPV1-specific blockers such as 4-(3-Chloro-2-pyridinyl)-N-[4-(1,1-dimethylethyl)phenyl]-1-piperazinecarboxamide (BCTC) and capsazepine. When capsaicin or gingerol was applied to wild-type cells in the presence of Ruthenium Red, a large proportion lost motility while flagella remained attached, suggesting that flagella stop contributing to motility, at least in part, through a TRP-channel-independent pathway. These results indicate that pungent compounds such as capsaicin and gingerol induce loss of flagellar motility and flagellar detachment in C. reinhardtii cells.