A conditioned supernatant from contains a powerful chemorepellent for wild-type cells, and a gene called is required for this response. This is the first genomic identification of a chemorepellent receptor in any eukaryotic unicellular organism. This conditioned supernatant factor (CSF) is small (<1 kDa), and its repellent effect is resistant to boiling, protease treatment, and nuclease digestion.
View Article and Find Full Text PDFThe swimming behaviors of Tetrahymena can be used in sensitive behavioral bioassays for estimating the effects of drugs, mutations, and other conditions on the physiological state of the cell. These assays can be used in both forward and reverse genetic approaches to help understand cellular functions from genotype to phenotype.
View Article and Find Full Text PDFAlthough G-protein coupled receptors (GPCRs) are a common element in many chemosensory transduction pathways in eukaryotic cells, no GPCR or regulated G-protein activity has yet been shown in any ciliate. To study the possible role for a GPCR in the chemoresponses of the ciliate Tetrahymena, we have generated a number of macronuclear gene knockouts of putative GPCRs found in the Tetrahymena Genome database. One of these knockout mutants, called G6, is a complete knockout of a gene that we call GPCR6 (TTHERM_00925490).
View Article and Find Full Text PDFLPA (lysophosphatidic acid), a known chemoattractant for many types of eukaryotic cells, is also a reliable chemoattractant for Tetrahymena. Since LPA receptors are GPCRs (G-protein coupled receptors) in many cell types and several putative GPCR sequences can be found in the Tetrahymena Genome Database, we are interested to determine whether similar GPCR pathways can be used for chemosensory transduction in Tetrahymena. To confirm our procedures, we tested the known chemoattractant proteose peptone (at 1.
View Article and Find Full Text PDFPurinergic Signal
June 2005
The unicellular ciliates Paramecium and Tetrahymena are the simplest eukaryotic cells to show reliable depolarizing responses to micromolar concentrations of external ATP and GTP. Their simplicity allows for combined analysis of swimming behavior, electrophysiology, receptor binding, behavioral mutant and drug screens as well as molecular genetic approaches such as RNAi and gene knockouts experiments. ATP and GTP are depolarizing chemorepellents in both ciliates, producing measurable receptor potentials and Ca(2+)-based action potentials that are correlated with jerking behaviors called avoiding reactions (AR).
View Article and Find Full Text PDFJ Eukaryot Microbiol
March 2008
The ciliates Tetrahymena and Paramecium respond to strong depolarizing stimuli with Ca(2+)-based action potentials, ciliary reversals, and consequent bouts of backward and forward swimming called "avoidance reactions" (ARs). We found that several representative tastants and odorants cause repetitive ARs in Tetrahymena and Paramecium at low (nM to microM) concentrations. Tetrahymena responded well to capsaicin, quinine, quinacrine, denatonium benzoate, eugenol, piperine, chloroquine, carvacrol, allyl isothiocyanate (AITC), and menthol.
View Article and Find Full Text PDFTetrahymena thermophila swims by the coordinated beating of hundreds of cilia that cover its body. It has been proposed that the outer arm dyneins of the ciliary axoneme control beat frequency, whereas the inner arm dyneins control waveform. To test the role of one of these inner arms, dynein heavy chain 7 protein (Dyh7p), a knockout mutant was generated by targeted biolistic transformation of the vegetative macronucleus.
View Article and Find Full Text PDFParamecium represents a simple, eukaryotic model system to study the cellular effects of some neuroactive drugs. They respond to the agonist beta,gamma-methylene ATP with a transient depolarizing receptor potential, Ca(2+)-based action potentials and repetitive bouts of forward and backward swimming called 'avoiding reactions' (AR). In vivo [(32)P]ATP binding assays showed saturable [(32)P]ATP binding with an apparent K(d) of approximately 23 nmol l(-1).
View Article and Find Full Text PDFCell Motil Cytoskeleton
December 2002
Cilia in many organisms undergo a phenomenon called ciliary reversal during which the cilia reverse the beat direction, and the cell swims backwards. Ciliary reversal is typically caused by a depolarizing stimulus that ultimately leads to a rise in intraciliary Ca++ levels. It is this increase in intraciliary Ca++ that triggers ciliary reversal.
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