A deletion common to two independently derived waxy mutations of maize

Abstract

A mutation at the maize waxy locus, wx1240, was isolated following treatment of pollen with EMS and self-pollinating ears on M1 plants. This allele was cloned and found to contain a 30-bp deletion within the gene and additional lesions upstream of the transcription start site. Using fine structure genetic mapping, we determined that the deletion is responsible for the mutant phenotype. In addition, the position of wx1240 on the genetic map coincided with the previously determined positions of two other waxy mutations, the spontaneous wx-C, which is reference allele, and the putative ethyl methanesulfonate (EMS)-induced wx-BL2. Molecular analysis of these alleles revealed that both contain the same deletion as wx1240, and that the wx-BL2 allele is similar to wx-C and possibly resulted from wx-C contamination. The deleted sequence responsible for these mutations is flanked by a short, 4-bp, direct repeat. Similar structures are favored sites for spontaneous deletions in other organisms. The data suggests that EMS is capable of inducing structural alterations in plant genes in addition to the point mutations normally ascribed to EMS-induced mutations.