Specific combinations of zein genes and genetic backgrounds influence the transcription of the heavy-chain zein genes in maize opaque-2 endosperms

The transcript levels of heavy-chain zein genes (zH1 and zH2) and the occur rence of the zH polypeptides in different opaque-2 (o2) lines were investig ated by RNA-blot analyses and by sodium dodecylsulfate-polyacrylamide gel e lectrophoresis or two-dimensional gel electrophoresis protein fractionation s. Four mutant alleles o2R, o2T, o2It, and o2-676 introgressed into differe nt genetic backgrounds (GBs) were considered. The mono-dimensional gel elec trophoresis zein pattern can be either conserved or different among the var ious GBs carrying the same o2 allele. Likewise, in the identical GB carryin g different o2 alleles, the zein pattern can be either conserved or differe ntially affected by the different mutant allele. Zein protein analysis of r eciprocal crosses between lines with different o2 alleles or the same o2 sh owed in some case a more than additive zH pattern in respect to the o2 pare nt lines. Electrophoretic mobility shift assay approaches, with o2-binding oligonucleotide and endosperm extracts from the above o2 lines, failed to r eveal o2-specific retarded band in any of the o2 extracts. The results sugg est that the promoter of some zH1 and zH2 contains motif(s) that can respon d to factors other than o2.