Abstract
Two lines of snapdragon, HAM2 and HAM5, have a transposon Tam3 at the same promoter site of the nivea (CHS) locus. In an inactive Tam3 state, HAM2 gives a light magenta petal color, while HAM5 shows white petals. The difference in the petal background colors is dependent on the nivea expression. The nivea expression in HAM5 was found to be repressed by the other Tam3 located 1.5 kb downstream of the polyA attachment site of nivea. The repression was not due to a kind of gene silencing mechanism such as PTGS and methylation, because the F1 plants of HAM2 and HAM5 showed their intermediate petal color phenotype, and no differenece was observed in methylation degree of their nivea sequences. Moreover, HAM5 often gave null phenotype of nivea in the progenies as a consequence of deletion of the chromosome segment that was induced by Tam3 transposition.
