Chemorepellent activity

Abstract: The chemotactic activity of the pathogen of bacterial wilt disease, Ralstonia solanacearum, was tested against 30 aromatic acids and plant hormones infused on filter discs in bioassays on agar plates. 4-Hydroxycinnamic acid ( p-coumaric acid) and 4-hydroxybenzoic acid were strong chemoattractants, 3,4-dihydroxybenzoic acid (protocatechuic acid) and jasmonic acid were weak attractants, and 2-hydroxybenzoic acid (salicylic acid) showed both attracting and repelling activity depending on dose. Examination of the dose dependency revealed that the ED50 for 4-hydroxycinnamic acid and 4-hydroxybenzoic acid was 0.08 and 0.39 μmol/disc, respectively. 2-Hydroxybenzoic acid showed chemoattractant activity at 0.33 μmol/disc but chemorepellent activity at 3.3 μmol/disc, and bacterial random motility was activated at 1.0 μmol/disc and bacterial activity was suppressed at 33 μmol/disc. Although water-soluble attractants including amino acids and organic acids have been previously investigated, this is the first report of hydroxylated aromatic acids (HAAs) as chemoattractants of R. solanacearum.

Abstract: Pituitary adenylate cyclase activating peptide (PACAP-38) is a peptide hormone which functions in many mammalian systems, including the nervous and digestive systems. Using in vivo behavioral studies, we have found that this hormone functions as a chemore-pellent in Tetrahymena thermophila with an EC50 of 10 nM. Cells previously adapted to PACAP-38 were found to be adapted to lysozyme and vice versa. Furthermore, the in vivo behavioral activity of PACAP-38 was blocked by addition of the anti-lysozyme receptor antibody, 5545. Chemorepellent activity of PACAP-38 was also inhibited by the addition of neomycin sulfate (inhibition constant Ki = 0.080 micromol x l(-1)), a competitive inhibitor of lysozyme binding to its receptor. PACAP-38 is a more potent and specific agonist for the lysozyme receptor than either intact lysozyme or CB2, a 24-amino acid fragment of lysozyme.

Abstract: Chemotactic properties of 3–7-mer peptides containing an EWS motive and their peptide amides synthesized and characterized by us were investigated in Tetrahymena pyriformis GL model. Analysis of the peptide acids shows that SEWS possesses exceptionally strong (660%±21; 430%±18) chemoattractant ability at 10−12 and 10−11m respectively. The shorter peptide (EWS) possesses chemorepellent activity, while longer peptides display neutral (WSEWS) or moderate chemoattractant (EWSEWS and GEWSEWS) chemotactic ability. Amidation of the C-terminus can significantly modify the character of peptides: it points to the conclusion that a free α-COOH group at this position is required for the high efficiency of SEWS, while in the shorter (EWS) and longer peptides (WSEWS and EWSEWS) amidation can result in chemoattractant ligands. Evaluation of the structure–function relationship of these compounds establishes the significance of Glu (E) with its high surface-exposed area and negatively-charged side chain. The high discriminative ability and good chemotactic responsiveness of Tetrahymena support the theory that a chemotactic signalling mechanism working in higher levels of phylogeny is a well conserved and inducible one even in protozoa. Copyright © 2002 John Wiley & Sons, Ltd.

Abstract: In this paper, the solid phase synthesis and chemical characterization of members of an SXWS sub-library (SAWS, SDWS and SKWS) as well as the comparison of their chemotactic properties with those of SEWS, which exhibits a prominent effect at 10−12M on a ciliated protozoan, Tetrahymena pyriformis, are described. We found that the chemotaxis of cells induced with the SXWS peptides varied according to the nature of the amino acid residue (Ala, Asp, Lys) in position X. The chemotactic activity of SEWS was not surpassed by any of three new tetrapeptides, although SAWS was also chemoattractant. Interestingly, SDWS, with an acidic side chain at position X, could not elicit any chemotactic response. SKWS, however, showed mild but significant chemorepellent activity over a wide concentration range. Chemotactic selection studies showed that the two chemoattractant peptides (SAWS and SEWS) had an expressed ability to select high-responder offspring cell populations. Peptides with neutral (SDWS) or chemorepellent (SKWS) properties were not able to select such subpopulations from the mixed cultures of Tetrahymena, indicating that the chemotactic response elicited by SXWS peptides is ligand-specific. For ligand-binding experiments N-terminally labelled fluorescent derivatives of SXWS peptides were prepared, applying [4-[7-hydroxycoumaryl]]acetic acid (Hca-OH) or 4-ethoxymethylene-2-[1]-naphthyl-5(4H)-oxazolone (naOx-OEt) as markers. Hca-OH was introduced using an active ester technique as the last step of SPPS, or after cleavage in solution. The oxazolone naOx-OEt reacted with the amino group of the peptide by liberation of EtOH. The binding characteristics of fixed Tetrahymena cells with the naOx-labelled peptides showed good correlation between binding profiles and chemotactic responsiveness (SEWS > SAWS > SDWS ∼ SKWS). A similar binding pattern was observed in the case of Hca-peptides (SEWS > SAWS > SDWS). Hca-SKWS, however, bound remarkably to the cell surface. The binding activity of the Hca-peptides was less pronounced than that of the naOx-peptides, indicating the importance of the fluorophores applied. Copyright © 2002 European Peptide Society and John Wiley & Sons, Ltd.