title: A soluble auxin-binding protein from cultured tobacco tissues stimulates RNA synthesis in vitro.
abstract: When the soluble auxin receptor from tobacco callus was isolated according to H. Oostrom et al. (1975, FEBS Lett. 59, 194-197; 1980, Planta 149, 44-47) a high polyphenol contamination in the receptor preparation was observed. We developed a new isolation procedure, which drastically reduced this contamination. The receptor, which was partially purified on Sephadex G-200, exhibited the same time- and temperature-dependent binding kinetics as described before (Oostrom et al. 1975, 1980). The Ka for indole-3-acetic acid (IAA) at 25°C was about 1.6·10(8) M(-1) and the number of binding sites varied from 0 to 2·10(-13) M mg(-1) protein. Addition of partially purified receptor preparations to isolated tobaccocallus nuclei resulted in an IAA-dependent stimulation of transcription, which was not observed with similar preparations that did not contain detectable amounts of specific IAA-binding sites. The average stimulation in the presence of 1 μM IAA was 42%; it was achieved by an increase in RNA-polymerase-II activity. The stimulation was not dependent upon the presence of 1 μM IAA during the isolation of the nuclei.
authors.affiliation: Department of Plant Morphogenesis, Botanisch Laboratorium, Rijksuniversiteit Leiden, Nonnensteeg 3, NL-2311 VJ, Leiden, The Netherlands.
authors.forename: P C
authors.initials: PC
authors.lastname: van der Linde
authors.forename: H
authors.initials: H
authors.lastname: Bouman
authors.forename: A M
authors.initials: AM
authors.lastname: Mennes
authors.forename: K R
authors.initials: KR
authors.lastname: Libbenga