This mutable allele is transactivated by an independently segregating En. In the absence of En, this allele shows a light pale phenotype in the aleurone. With En, the kemel phenotype is a coarse, early mutating type with a colorless background. This indicates that this allele is a2-m(r-pale) responding to En to yield coarse mutability.
In backcross progeny kernels with [a2-m(r-pale) Bt/a2 bt X a2 bt/a2
bt] a changed mutable phenotype arises that has a very late fine mutability
pattern. In further tests of these exceptional kernels, a single factor
modifying the coarse expression of the a2-m(r-pale) can be identified.
The segregation pattern indicates that the "fine factor" (F) does not have
the transactive En excision function but can modify the En that causes
the coarse expression. The hypothesis for this series of interactions with
a2-m(r-pale) is as follows:
|+||+||= fine mutability|
|+||-||= coarse mutability|
|-||+||= pale - no mutability|
|-||-||= pale - no mutability|
The F factor is similar in activity to other modifiers, as En-Malt.
Peter A. Peterson
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