High chlorophyll flourescent (hcf) mutants of higher plants represent a class of nuclear genes required for the development of photosynthetically active chloroplasts. Their products may include nuclear-encoded components of the photosynthetic apparatus, as well as enzymes and regulatory genes required for co-factor biosynthesis and plastid gene expression. Some hcf mutants have pleiotropic effects on membrane protein assembly and thylakoid organization. hcf106 is an example of such a mutation in maize: The Hcf106 gene has been cloned by transposon tagging, and the gene product shown to be an integral chloroplast membrane protein. It has a single transmembrane domain, a potential nucleotide binding site, but no other homology to known proteins. Thylakoid membranes from mutant chloroplasts have lost their characteristic lateral heterogeneity, and fail to accumulate a subset of thylakoid membrane proteins. Analysis of derivative alleles, hypoploids and double mutants will be used to genetically define the hcf106 lesion. Immunolocalization by suborganellar fractionation and immuno- electron microscopy will be used to investigate the possible roles of this protein in thylakoid assembly. %%% Photosynthesis is the basis of life on the planet Earth and a complete understanding of the process as well as chloroplast biogenesis is one of the most important goals of biological research.
