Analysis of mitochondria to nucleus signaling affecting flower development in carrot

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Mutations in plants can lead to altered flower morphologies, or homeosis.  For example, petals can be replaced by sepals and pollen-producing stamens can be replaced by petals.  A comprehensive nuclear genetic model for flower development has been derived for Arabidopsis, and orthologues of critical genes can be identified in other species.Homeotic phenotypes are observed in carrot, but in contrast to nuclear gene control in Arabidopsis, the mutation in carrot is conditioned by a cytoplasmic factor, likely in the mitochondrion.  The occurrence of  cytoplasmic homeosis suggests that cytoplasmic-nuclear signaling occurs in flower development. The research proposed here will work towards the development of a genetic pathway for this process, which has not been elucidated in any plant species.Carrot can serve as a novel model system because the cytoplasmically-controlled homeotic phenotypes evolved in natural populations and inbred lines are available with distinct nuclear-cytoplasmic interactions: the replacement of stamens with petals, or both petals and stamens with bract-like organs.  The phenotypes result from two nuclear genotypes interacting with one cytoplasmic accession.  In other species, the cytoplasmic regulation of flower development results from backcrossing into alien cytoplasms or protoplast fusion, and distinct phenotypes related to specific cytoplasmic-nuclear interactions are not clearly observed, as in carrot.The long-term objective of this research is to discover all the genetic components important for mitochondria to nucleus signaling affecting flower development.  Ultimately, the research program could directly link expression of a mitochondrial factor to orthologs of genes in the Arabidopsis floral development model, advancing basic knowledge in an emerging area of plant biology.  In the short term, genes related to redox will be studied, and differential gene expression assessed, in floral meristems of cytoplasmic mutant and wild type carrot lines.