Preliminary mapping and biochemical analysis of opaque8
--G. I. Graham, J. Suresh and R. L. Phillips

The opaque endosperm mutations in maize have been valuable for elucidating the control of kernel storage proteins, as well as providing sources of improved nutritional quality. Here we describe another opaque mutant named opaque8. Seed for this study was provided by Dr. O. E. Nelson, OE, Jr. in an unknown inbred background. The phenotype is controlled by a single recessive gene; segregation on a B73 x o8 F2 ear was 174 normal:57 opaque. RFLP mapping based on 20 F2 opaque individuals indicates the gene is 2.5 map units away from the sequence detected by umc134 on chromosome 2. Opaque8 appears to be between umc131 (12.5 map units) and bnl12.09 (7.5 map units). The order of the 3 marker loci is:

 bnl12.09--------------umc134-------------umc131
                         5                              10

The exact location of o8 in reference to umc134 has not yet been determined. This mutation, like other opaques, appears to increase lysine. Because the background was unknown, we analyzed F2 kernels of crosses of o8 and B73, A619, and A188. Kernels were separated based on phenotype (opaque vs. normal), pooled, and ground together. Preliminary evidence indicates that the o8 sample had higher lysine levels by 10.8, 11.7, and 13.0% for the B73, A619, and A188 backgrounds, respectively. Zein protein levels did not appear to be different for either the B73 or A619 backgrounds. However, in the A188 background, the o8 zein-2 protein fraction was significantly lower than the normal counterpart. Isoelectric focusing (IEF) and SDS-PAGE showed no particular zein proteins to be absent. 


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