GENOMICS AND MORPHO-DEVELOPMENTAL CHARACTERIZATION OF PLASTIDS IN ROSACEAE

Scott Michael Schaeffer

The Rosaceae family represents many diverse and economically important species, several of which have recently been sequenced. Historically, plastids and their multifarious functions have received insignificant attention in Rosaceae. Research in this dissertation addresses this fundamental knowledge gap by: (1) Performing a morpho-developmental characterization of fruit plastids in </italic>Malus × domestica</italic> Borkh. (apple) as a representative model using electron microscopy. It was observed that apple fruit plastids differ from model systems and developmental transitions follow a distinct pathway in the epidermis and collenchyma. These observations indicate presence of complex metabolic processes that may be unique to apple and Rosaceae in general; (2) Establishing a workflow and knowledge base of predicted plastid-targeted proteomes in </italic>Malus × domestica</italic> Borkh., </italic>Prunus persica</italic> (peach), and </italic>Fragaria vesca</italic> (strawberry) representing three important Rosaceae sub-families and, comparing them to four other model systems. Analysis of the predicted plastid-targeted proteomes in </italic>Malus × domestica</italic>, </italic>Prunus persica</italic> and </italic>Fragaria vesca</italic> revealed a significant proportion of genomes encode for plastid-targeted proteins, several of which lack identity to plastid-targeted proteins in other species. Comparative analysis with other species revealed significant subsets of genes exclusive to each species and identification of homologs that may be alternatively targeted either to the chloroplast or the cytosol depending on the species; (3) Identifying differentially expressed genes between `Honeycrisp' and `Golden Delicious' apples using a small scale comparative transcriptome profiling approach between peel and core tissue of `Golden Delicious' and `Honeycrisp' genotypes to evaluate the spatio-temporal expression of predicted plastid-targeted proteins. A total of 115 differentially expressed fragments mapped back to 44 genes, many known to be implicated in important fruit traits; and, (4) Functional and phenometric characterization of one of the plastid localized calcium channel proteins from apple (MdPBAG) and its homologs spanning </italic>Arabidopsis</italic> (AtALB3), </italic>Nicotiana</italic> (NtPPF), cyanobacteria (YidC) and </italic>E. coli</italic> (YidC) by engineering the genes into the tobacco chloroplast genome. Serendipitous overexpression of the N-terminal region of the apple homolog resulted in abnormal granum stacking in the plastids, delayed flowering, reduced plant height, high F<sub>0<sub> levels and enhanced oxidation of quinone in the linear electron flow photosynthetic chain.

GENOMICS AND MORPHO-DEVELOPMENTAL CHARACTERIZATION OF PLASTIDS IN ROSACEAE

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