Submitted to: PLoS One
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/12/2010
Publication Date: 3/29/2010
Citation: Velten, J.P., Cakir, C., Cazzonelli, C.I. 2010. A spontaneous dominant-negative mutation within a 35S::AtMYB90 transgene inhibits flower pigment production in tobacco. PLoS ONE. 5(3):e9917. Interpretive Summary: A single mutation converted a gene that normally enhances plant pigment production into a gene that now interferes with pigment production. Analysis of the mutation and expression of the mutant gene provides useful insight into the molecular mechanisms of gene regulation in plants.
Technical Abstract: A spontaneous mutation converted a hyper-pigmented (anthocyanins), CaMV-35S-pro::AtMYB90 containing, transgenic tobacco line into one displaying wild-type pigmentation in all tissues except for flower petals, which, counter-intuitively, showed anthocyanin levels dramatically below wild-type in the presence of the mutant allele. The resulting dominant-negative white flower mutant (PGW) was subsequently found to be the result of a single base change within the AtMYB90 transgene that converts lysine-172 to a nonsense codon (AAG->TAG) and removes 78 amino acids from the C-terminus of the wild-type protein. Comparison of expression profiles for the PGW allele, it’s wild-type progenitor (AtMYB90) and a flower-specific tobacco R2R3-myb homolog (NtMYB141), support a model in which the truncated PGW protein acts as a competitive inhibitor of the endogenous tobacco myb transcription factor responsible for flower color. The PGW phenotype is similar to that previously reported for tobacco plants that over-express either the maize CI-1 dominant-negative anthocyanin regulatory mutant, or a wild-type strawberry myb factor that controls fruit anthocyanin production. Comparison of the predicted PGW protein to these, and other related anthocyanin regulatory myb proteins, provides useful insight into the function of R2R3 myb transcription factors in plants.