However, the R-ch region corresponding to S2 is disrupted at the beginning of Intron2. Only the S1 coding region is functional. The P-like promoter drives expression from S1 and sigma behaves genetically as a bidirectional promoter for aleurone pigmentation. Nevertheless, sigma has a stronger effect in the S1 direction and weaker towards S2. These alleles lack all plant color, but have weak aleurone pigmentation.
Pale derivatives revert to full R-ch with about the same frequency as the forward mutation rate.
Southern blot analysis demonstrated that the R-ch instability is a result of an internal C.O. and not an epigenetic event.