MOLECULAR-CLONING AND EXPRESSION PATTERNS OF 3 ALLELES OF THE DEFICIENS-HOMOLOGOUS GENE ST-DEFICIENS FROM SOLANUM-TUBEROSUM

Three alleles of the Deficiens-homologous potato gene St-Deficiens (St -Def) present in the genome of a tetraploid Solanum tuberosum variety were isolated and characterized. For one allele (St-Def pD13) the comp lete molecular structure was determined by sequence analysis and compa rison with its cDNA, while for the other two alleles (pD10, pD12) only partial sequences of regulatory and coding regions were obtained. All three alleles showed (except for one amino acid exchange in pD10) ide ntical sequences in the coding region. While sequence variation was ob served within the respective promoters starting some 300 nt upstream o f the putative transcriptional start site, the 3' terminal promoter se quences were highly conserved. Within this region, a sequence of 81 nt was identified which showed 73% sequence identity to a corresponding sequence in the Deficiens promoter. This region which contains a putat ive serum response element was previously shown to regulate the expres sion of the Deficiens gene in Antirrhinum majus. Expression patterns f or the three alleles in transgenic potato lines expressing St-Def prom oter/Gus constructs were identical. GUS activity was predominantly loc ated in petals and stamens as expected for the activity of a Def-homol ogous gene, but a significant level of expression was also detected in the ovary wall and in the vascular bundles supporting anthers and pet als. The promoters were also active in abscission structures at the ju nction of flower stem and pedicel, as well as in anther stomium.