Moeller, Claudia , Wanke, Dierk , Harter, Klaus , Dilkes, Brian , Feldmann, Ken , Schulz, Burkhard .
Analysis of an epigenetic suppressor of the Arabidopsis twisted dwarf1 (twd1) mutation.
The TWISTED DWARF1 (TWD1)/AtFKBP42 gene of Arabidopsis encodes a immunophilin-like protein which interacts with plasma membrane ABC transporters AtPGP1 and AtPGP19. This leads to regulation of polar auxin transport facilitated by ABC transporters. Null mutants of AtFKBP42 are characterized by dwarfism due to impaired cell elongation and disoriented cell growth, coining the name twisted dwarf1 (twd1) for the gene. A suppressor mutant screen resulted in twd1-sup which is a suppressor mutation of the T-DNA induced twd1-2 knock-out allele. The phenotype of twd1-sup is intermediate between twd1-2 knock-outs and wild-type (Ws-2). Genetic analysis showed dominance of the suppressor mutation over twd1-2. Segregation ratio of phenotypes from crosses of wild-type and twd1-sup provides strong evidence for an intragenic suppressor. However, no sequence alterations of the TWD1 locus could be found in knock-out and suppressor lines. The NPTII marker of the inserted T-DNA is silenced in twd1-sup plants but not in twd1-2. This reduction of NPTII expression can be overcome by treatments with the methylation inhibitor 5-azacytidine (5-azaC). In addition, prolonged treatments of suppressor plants with 5-azaC caused reversion of the intermediate suppressor phenotype back to the phenotype of knock-out plants. The same phenomenon has been observed in crosses with methylation mutants such as ddm1, met2 and hog1. Bisulfite sequencing of the TWD1 locus in twd1-sup and twd1-2 shows strong DNA methylation of the NPTII gene in twd-sup but not in the null mutant line. In twd-sup a very low level accumulation of the full length mRNA of the TWD1 gene could be detected which has never been the case for twd1-2. We will present a model for methylation-dependent regulation of the TWD1 gene in twd1-sup.
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1 - University Tuebingen, ZMBP
2 - UC Davis, Genome Center
3 - Ceres Inc., Research
4 - Purdue University, Horticulture and Landscape Architecture, 625 Agricultural Mall Drive, West Lafayette, IN, 47907, USA
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM