FIG. 1.

Overview of the Chs silencing and nonsilencing T-DNA loci examined in this study. The Chs transformants and the identification of Chs silencing IR loci and the nonsilencing S loci present in these plants have been described previously (63, 69). All T-DNA constructs used in this study contained the neomycin phosphotransferase selectable marker gene (nptII) driven by the nopaline synthase promoter (Nos). The T-DNAs of the PSE6 and PSE19 transformants contained a CaMV-35S promoter-driven chimeric gene composed of the uidA coding region fused to the 5′ half (PSE6) or the full-length (PSE19) ChsA cDNA. The T-DNA of the PSE21 transformants contains the full-length ChsA cDNA. The small arrows in the maps indicate the transcription start sites of the Nos promoter and CaMV-35S promoter. These transgenes are flanked by the 3′nos polyadenylation region, which is indicated by a small open box. The arrowheads flanking the nptII and (uidA-)ChsA transgenes indicate the right and left border of the T-DNAs, respectively. The arrows below the maps of the silencing loci depict the palindromic arrangement of the integrated T-DNAs. The dashed lines indicate flanking plant DNA. Chs silencing by the IR loci in homozygous plants is stronger than in hemizygous plants, as indicated to the right of the physical maps (−, no silencing; +, most corolla limbs contain ≤5% white tissue; ++, about 5 to 50% white tissue; +++, about 50 to 95% white tissue; ++++, >95% white tissue; nd, not determined). pBin19, cointegrated pBin19 vector DNA.