A Spontaneous Dominant-Negative Mutation within a 35S::AtMYB90 Transgene Inhibits Flower Pigment Production in Tobacco
Background
In part due to the ease of visual detection of phenotypic changes,
anthocyanin pigment production has long been the target of genetic and
molecular research in plants. Specific members of the large family of plant
myb transcription factors have been found to play critical roles in
regulating expression of anthocyanin biosynthetic genes and these genes
continue to serve as important tools in dissecting the molecular mechanisms
of plant gene regulation.
Findings
A spontaneous mutation within the coding region of an Arabidopsis
35S::AtMYB90 transgene converted the activator of
plant-wide anthocyanin production to a dominant-negative allele (PG-1) that
inhibits normal pigment production within tobacco petals. Sequence analysis
identified a single base change that created a premature nonsense codon,
truncating the encoded myb protein. The resulting mutant protein lacks 78
amino acids from the wild type C-terminus and was confirmed as the source of
the white-flower phenotype. A putative tobacco homolog of
AtMYB90 (NtAN2) was isolated and found
to be expressed in flower petals but not leaves of all tobacco plants
tested. Using transgenic tobacco constitutively expressing the
NtAN2 gene confirmed the NtAN2 protein as the likely
target of PG-1-based inhibition of tobacco pigment production.
Conclusions
Messenger RNA and anthocyanin analysis of PG-1Sh transgenic lines (and PG-1Sh
x purple 35S::NtAN2 seedlings) support a model in which the
mutant myb transgene product acts as a competitive inhibitor of the native
tobacco NtAN2 protein. This finding is important to researchers in the field
of plant transcription factor analysis, representing a potential outcome for
experiments analyzing in vivo protein function in test
transgenic systems that over-express or mutate plant transcription
factors.
For the full article visit: A Spontaneous Dominant-Negative Mutation within a
35S::AtMYB90 Transgene Inhibits Flower Pigment Production
in Tobacco
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