In this proposal Dr. McCarty explores the regulatory mechanism which controls and integrates expression of diverse developmental responses related to seed maturation in maize. Mutations in the Viviparous-1 (Vp-1) gene block much or all of maturation related gene expression in embryo and aleurone tissues of the developing seed. Two seemingly unrelated groups of genes are regulated by Vp1: 1) An embryo maturation set including various late embryogenesis abundant genes (LEA's) and the 7s globulin genes. These genes are also regulated by the hormone, abscisic acid. 2) The second set includes the genes of the anthocyanin pathway. Dr. McCarty has shown that Vp1 activates the anthocyanin pathway by activating a second regulatory gene, C1. Thus, these genes function as a regulatory hierarchy. His results suggest that Vp1 is a novel transcription factor. By expressing the Vp1 gene in maize protoplasts, he is able to characterize regulatory sequences involved in regulation of C1 and Em, a LEA gene of wheat. This system also provides a functional assay for the Vp-1 protein. His objectives are to 1) Determine how Vp-1 regulates transcription of target genes, 2) Use mutagenesis to define functionally important sequences in the Vp1 protein, 3) Identify factors that interact with Vp1, 4) Characterize Vp1's role in development using ectopic expression and 5) Characterize transcriptional and post-transcriptional regulation of Vp-1 expression.
