October 2, 2003, 4PM, Tuesday 
1352 Gilman Hall   

["p1 maize locus pleiotropy"]

Dr. Thomas Peterson
Associate Professor
Pioneer Hi-Bred International Chair in Maize Molecular Genetics
Departments of Zoology & Genetics, and Agronomy 
Iowa State University, Ames

Our work on the maize p1 locus, which controls red phlobaphene pigmentation of kernel pericarp and cob, has disclosed some interesting pleiotropic effects.  Ordinarily we think of "color genes" as controlling secondary metabolic pathways with little effect on plant morphology.  What we have observed with both natural alleles and transgenes, is that mis-expression in vegetative tissues causes a host of abnormalities, including short stature and leaf rolling.  Over-expression in floral organs is associated with a defect in release of pollen, and most strikingly abnormal shaped kernels (pointy).  Actually I think these effects are caused by toxicity of the pigments or pigment precursors to growing cells; in the case of the kernels, the pointy shape reflects the shape of the pre-fertilized kernel, and over-expression of the phlobaphene precursors causes premature cell death and "freezing" of the kernel pericarp into the shape present at early development.

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