Photoautotrophic Chenopodium rubrum Cell Suspension Cultures Resistant against Photosynthesis-Inhibiting Herbicides I. Selection and Characterization

Jutta Thiemann and Wolfgang Barz Institut für Biochemie und Biotechnologie der Pflanzen, Westfälische Wilhelms-Universität, Hindenburgplatz 55, D-48143 Münster, Bundesrepublik Deutschland Z. Naturforsch. 49 c, 186-194 (1994); received June 25/December 16,1993 Herbicide Resistance, Selection Mechanism, Photoautotrophic Cell Culture, Chenopodium rubrum For establishing metribuzin-resistant, photoautotrophic Chenopodium rubrum cell cul­ tures plated cells, callus cultures or suspension cultures were subjected to selection proce­ dures. The most effective procedure was the stepwise increase in the concentration of the herbicide from 0.01 îm to 10 îm in suspension cultures, which resulted in the isolation of eight different metribuzin-resistant photoautotrophic cell lines. Conjugation metabolism or a decrease in the uptake and translocation of the selective agent were not responsible for resist­ ance, which was stable in the absence of the inhibitor over numerous growth cycles. Meas­ urements of the photosynthetic electron transport, analyses of fluorescence induction kinetics and determination of the binding properties of 14C-labelled metribuzin to isolated thylakoids indicated that resistance of the cell lines is based on an alteration in the photosystem II her­ bicide-binding protein (D 1 protein). RFLP analysis of the psbA gene of the eight resistant cell lines demonstrated that none of them possess an amino acid exchange in position 264 of the D 1 protein leading to altered herbicide-binding properties.