COORDINATED TRANSCRIPTIONAL REGULATION OF STORAGE PRODUCT GENES IN THE MAIZE ENDOSPERM

We have demonstrated that expression of genes involved in starch and s torage protein synthesis of the maize (Zea mays L.) endosperm are coor dinated. Genetic lesions altering synthetic events in one biosynthetic pathway affect expression of genes in both pathways. Initial studies focused on shrunken2 (sh2) and brittle2 (bt2) mutants because these ge nes encode subunits of the same enzyme, ADP-glucose pyrophosphorylase. Analysis of various sh2- and bt2- mutant alleles showed that the most severe mutations also conditioned the largest increase in transcripts . The analysis was extended by monitoring the transcripts of the genes , shrunken I (sh1, structural gene for Suc synthase), sh2 bt2, waxy1 ( wx1, structural gene for starch synthase), and those of the large and small zeins in isogenic maize lines at 14, 22, and 30 d postpollinatio n. Endosperms were wild type for all of these genes or contained sh1-, sh2-, bt1-, bt2-, opague2 (o2-), or amylose-extender1 (ae1-) dull1 (d u1-) wx1- mutations. Transcripts increased continually throughout kern el development in the mutants relative to the standard W64A used. Vari ation in the amount of Suc entering the developing seed also altered t ranscript amounts. The results indicate that starch and protein biosyn thetic genes act in a concerted manner, and both are sensitive to muta tionally induced differences.