- Saintpaulia (African violet) pigmentation is notoriously unstable and sometimes forms white stripes, particularly following passage through tissue culture. White-striped petals were thought to be due to periclinal chimeras, but we confirmed that white stripes result from epi-genetic regulation rather than periclinal chimeras based on the flower color traits of plants obtained from tissue culture.
- Gene expression in several plant lines, anthocyanin quantification, bisulfite sequencing, and methylation analyses were used to demonstrate the presence of a single MYB gene responsible for pigment variation. We identified SiMYB2 as the cause of variations in tissue color patterning, and that two RNAs were generated from SiMYB2.
- SiMYB2-Long was expressed in colored tissues, while SiMYB2-Short was expressed only in noncolored tissues. Functional analyses revealed that SiMYB2-Long is an anthocyanin bio- synthesis activator and SiMYB2-Short is nonfunctional. Exon 3 of SiMYB2 was generated by the insertion of a transposon-like sequence. A mutant lacking the element was obtained from cultivars with noncolored tissues. Anthocyanin content and SiMYB2-Long expression in the mutant were greatly increased compared to wild-type.
- Our results suggest that the white-striped petals of Saintpaulia are not formed by periclinal chimeras but through the transcriptional selectivity of epigenetically regulated SiMYB2.
Abstract