Induction of unstable alleles at the temperature-sensitiveVirescent-1gene of maize using the transposable elementDissociation

Abstract

SummaryTranspositive mutagenesis was employed to prepare genetic strains useful in cloning theVirescent-1locus (V1) of maize. A stepwise approach was used based on: (1) the isolation of putative insertion phenotypes (62 cases); (2) the verification of the genetic nature of the selected events (36v1-mmutant alleles induced); (3) the accurate genetic study of 11 alleles; (4) the genetic assessment that the allelesv1-m1andv1-m4are due to the insertion ofa Dselement into the locusV1; (5) the proof that aDs-like DNA element induces the inactivation of the wild type function in the allelev1-m1. The phenotype of the unstable alleles, studied by germinating and keeping maize seedlings at the temperature of 18 °C, are the following: allelesv1-m1, v1-m9, v1-m11, v1-m17andv1-m18showing a few revertant green sectors on their leaves;v1-m4exhibiting a reverse type of variegation; allelesv1-m2andv1-m13with a coarse pattern of variegation; allelesv1-m12, v1-m21andv1-m23frequently showing leaves part green with white stripes and part white with green stripes. For the alleles studied, in addition to somatic instability, germinal reversions also occurred. In some cases, these reversions resulted in stable derivatives with a different colour from that of the wild-type (‘near green’ or pale phenotypes). The results presented not only allow thev1-m1allele to be chosen as a starting material for cloning theV1locus, but also define the molecular strategy to be followed.