MUTATIONS CONFERRING LINCOMYCIN, SPECTINOMYCIN, AND STREPTOMYCIN RESISTANCE IN SOLANUM-NIGRUM ARE LOCATED IN 3 DIFFERENT CHLOROPLAST GENES

A number of Solanum nigrum mutants resistant to the antibiotics specti nomycin, streptomycin and lincomycin have been isolated from regenerat ing leaf strips after mutagenesis with nitroso-methylurea. Selection o f streptomycin- and spectinomycin-resistant mutants has been described earlier. Lincomycin-resistant mutants show resistance to higher level s of the antibiotic than used in the initial selection, and in the mos t resistant mutant (L17A1) maternal inheritance of the trait was demon strated. The lincomycin-resistant mutant L17A1 and a streptomycin plus spectinomycin resistant double mutant (StSp1) were chosen for detaile d molecular characterisation. Regions of the plastid DNA, within the g enes encoding 16S and 23S rRNA and rps12 (3') were sequenced. For spec tinomycin and lincomycin resistance, base changes identical to those i n similar Nicotiana mutants were identified. Streptomycin resistance i s associated with an A --> C change at codon 87 of rps 12 (converting a lysine into a glutamine), three codons upstream from a mutation earl ier reported for Nicotiana. This site has not previously been implicat ed in streptomycin resistance mutations of higher plants, but has been found in Escherichia coli. The value of these mutants for studies on plastid genetics is discussed.