Three regulators of the maize anthocyanin pathway

The maize anthocyanin pathway provides an excellent system for investigating the control of gene expression, as the red and purple products are visible, and nonessential. Factors responsible for the transcriptional regulation of the biosynthetic genes required for production of the anthocyanin end products, include the b1/r1 bhlh and c1/pl1 myb genes that are expressed in a tissue specific manner and subject to epigenetic control. My project was to investigate three additional regulators of the anthocyanin pathway, mop1, pac1 and a3.; Chapter II describes mediator of paramutation 1 ( mop1) effects on the epigenetic phenomenon known as paramutation. These effects are shown to be specific for certain epigentically regulated alleles of the b1, r1 and pl1 loci, illustrating that mop1-1 is not a general regulator of anthocyanin genes. In chapter III, mop1 effects are extended to the maintenance of epigenetic silencing of Mutator transposable elements. We hypothesize that mop1 encodes a chromatin remodeling protein.; The pale aleurone color 1 (pac1) locus examined in chapter IV, was previously identified as a regulator of anthocyanin biosynthetic gene expression in the aleurone. Mutants in pac1 did not affect the expression of the other regulatory genes. I cloned pac1, showed it encoded a WD40 repeat protein, complementated mutants in the Arabidopsis ortholog ttg1, cloned the genomic sequence of a homologous locus, mp1, and examined the evolutionary relationship of these and related plant and animal homologs.; Effects of a3 as a recessive modifier of anthocyanin pigmentation were previously described. In chapter V, I extended the previous genetic analysis of a3 showing interactions with additional alleles of the b1 and r1 regulatory loci and established, through molecular experiments, that a3 effects were due to the negative modification of transcription and RNA levels of the anthocyanin biosynthetic genes.; This dissertation includes both my previously published and my co-authored material (chapters II and III). Others have contributed to the work in chapters IV and V, however, it was principally the work and responsibility of this author.