Lack of evidence for antisense suppression in the fungal plant pathogen Ustilago maydis

Modulation of the expression of the Ustilago maydis Pyr3 gene, encoding dih ydroorotase (DBOase), through antisense RNA regulation has been explored. T his was done by placing the gene in sense and antisense orientations under the control of an hsp70-like gene promoter in a high-copy number autonomous ly replicating expression vector. Cells transformed with the antisense vect or contained similar levels of DBOase activity to those found in cells harb oring the expression vector alone. Transformants containing the antisense v ector did not exhibit uridine-dependent growth, which would be expected for a Pyr3-deficient phenocopy. This was despite detection of high levels of a ntisense RNA transcripts in cells transformed with the Pyr3 antisense vecto r.