SummaryBacteria communicate with each other in a population density-dependent process known as quorum sensing. N-acyl-homoserine lactones (HSLs) are the autoinducers of Gram-negative bacteria and the best-studied quorum sensing signals so far. HSLs induce various responses in plants, including systemic resistance and root development.Here, we used different methods, including tritium labelling, sensor strain assays and monoclonal antibodies (mAbs), to analyse the uptake and translocation of C8-and C10-homoserine lactones into barley (Hordeum vulgare cv Barke).Both HSLs were already systemically transported into the shoot at 2 h after application. HSL uptake could be inhibited by orthovanadate, demonstrating that ABC transporters are involved in the uptake. Root transport occurs predominantly via the central cylinder, which was shown by transport inhibition via KCl application and autoradiography of root cross-sections. Furthermore, a newly established detection method with mAbs allowed the first detection of a systemic transport of long-chain HSLs in plants.The coupled use of different HSL detection methods demonstrated that the uptake and transport of HSLs into barley does not occur passively, but relies, at least partially, on active processes in the plant.
A selective enzyme-linked immunosorbent assay for 1-naphthol was developed. Eight rabbits were immunized with either [(5-hydroxy-2-naphthylenyl)oxy]acetic acid (2b)-BSA, [(5-hydroxy-1-naphthylenyl)oxy]acetic acid (4)-BSA, or 5-hydroxy-2-naphthoic acid (7)-KLH, and all sera were screened against 14 different coating antigens. From this screening procedure, five assays could be developed, using two 7-KLH antisera, 3907 and 3909. The assay with the least interference and the best reliability (7-KLH antiserum 3907, 1:9000, and coating antigen 2b-BSA, 1.5 gg/mL) was further optimized and characterized. It showed an I50 value of about 72 gg/L, with a range of detection from 10 to 1000 gg/L. There was no cross-reactivity with carbaryl, which makes this assay very suitable for the selective detection of 1-naphthol, for example, in undiluted human urine and in soil extract. The assay was tested in organic solvents and showed a tolerance of at least 10 % solvent (acetone, acetonitrile, methanol).
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