Understanding leaf morphology: A molecular genetic approach to address the mechanisms involved in establishing and maintaining a multicellular leaf.

摘要

n important question in developmental biology concerns the mechanisms by which a few cells coordinate division and differentiation to yield the complex structures and organs found in multicellular organisms. During vegetative growth in plants, cells in the apical meristem must coordinate division and differentiation to yield the fully mature leaf organ. Alterations in these processes may result in an abnormal leaf. Two approaches are taken in this dissertation that may serve as a foundation to explore and better understand these developmental processes in plants.;The first approach is the isolation and characterization of an EMS-generated, cold-temperature sensitive mutation in Arabidopsis thaliana, designated lem7 (leaf morphogenesis). When grown at 16;Previous studies have shown that transcription factors may play a role in vegetative development. One such transcription factor is the KNOTTED-1 homeodomain protein from maize. Ectopic or overexpression of KN1 has been shown to alter leaf morphology in maize and several other plants. Nuclear localization has been shown to regulate the activity of several transcription factors. Furthermore, in situ and immunolocalization studies have suggested that KN1 may be regulated by its sub-cellular location. Therefore, identification of nuclear localization signals in the KN1 protein may provide information on the regulation of KN1 transcription factor activity. In this dissertation, the ability of the KN1 homeodomain and the highly conserved proximal amino acid residues (the ELK region) to serve as nuclear localization signal sequences are analyzed. The ELK homeodomain (ELK-HD) of KN1 was fused to the reporter gene uidA encoding the bacterial enzyme