c2-m881058Y - an example of three factor control

--Michael G. Muszynski and Peter A. Peterson

The c2-m881058Y allele (MNL 64:9) was previously shown to be non-autonomously controlled. To investigate the relationship to En(Spm), this mutant was crossed to a colored wx line. The F1 (C2/c2-m Wx/wx) was backcrossed to a c2/c2 wx-m8/wx-m8 tester . The results from these crosses indicate that En was present. If En is responsible for the c2-m mutability, then all spotted kernels should also be wx-mutable (wx-m) and all colorless kernels should be wx-stable (wx-st). If the En is unrelated to the c2-m and another factor is controlling spotting, there should then be no correlation between spots and wx mutability. The expected results if En is unrelated and the observed results are summarized as follows:
 
   
Expected
Observed
En Factor c2-m wx-m8 c2-m wx-m8
+ + sp wx-m sp wx-m
+ - cl wx-m cl wx-m
- + sp wx-st cl wx-st 
- - cl wx-st cl wx-st 

There are several interesting features here. All spotted kernels are wx-mutable, but the presence of the colorless wx-mutable class indicates that En alone is unable to trigger spotting. Further, the lack of a spotted wx-stable class indicates that a separate factor alone is also not able to trigger spotting. Therefore, this unstable allele requires En and an independent factor. It may be jointly controlled. This would be the first instance of three factor control (the locus, En and a non-En factor) of mutability. Tests to confirm this hypothesis are underway.


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