Ultraviolet mutagenesis and genetic analysis of resistance to methylglyoxal-bis (guanylhydrazone) in tobacco

Summary

We have isolated cell lines of Nicotiana tabacum resistant to methylglyoxal-bis(guanylhydrazone) (MGBG), a potent inhibitor of S-adenosylmethionine decarboxylase. We obtained 31 resistant lines from ultraviolet light mutagenized cultures, representing at least 13 independent events. No resistant lines were obtained from non-mutagenized control cultures. The increase in mutation rate due to the ultraviolet light treatment was 22 to 62 fold increased over an estimate of the maximum possible spontaneous rate. In reconstruction experiments we reselected resistant cell lines from varying dilutions into a background of a constant concentration of wild type cells; at the minimum ratio of resistant cells to wild type cells, 1:125,000, we recovered resistant colonies at an estimated plating efficiency of 12.5%. A number of resistant lines have been regenerated into plants. All of the ones that flowered are male sterile, sometimes associated with morphological transformations. Some are female sterile as well. Meiotic genetic analysis of one resistant line, Mgr12, suggests that the MGBG resistance is segregating as a nuclear dominant trait. The male sterility and abnormal floral development of Mgr12 cosegregate with the MGBG resistance, suggesting the two phenotypes are coincident.