In plants, the synthesis of isoprenoids and isoprenoid-related compounds such as chlorophyll, carotenoids, tocopherols, phytoalexins, and gibberellins require the GERANYLGERANYL DIPHOSPHATE SYNTHASE (GGPPS) gene family. In Arabidopsis thaliana (At), a point mutation in one member of this family, ggpps11, results in rounded, variegated rosette and cauline leaves with irregular margins. The variegation patterning is typically reproducible, with the center of the leaves being albino and the periphery phenotypically wild type. We have compared the transcriptome of wild type, ggpps11 white sectors, and ggpps11 green sectors. This analysis revealed a group of twelve Berberine Bridge Enzyme-like (BBE-like) proteins which are differentially regulated between the two mutant tissues. Although At does not produce endogenous berberine, exogenous application of berberine leads to pointy leaves, likely resulting from inhibition of adaxial cell differentiation by berberine, causing the leaf-polarity defects. To identify how these genes are involved in leaf development and polarity, T-DNA lines with individual mutations in the BBE-like genes were identified and obtained as segregating populations from the Arabidopsis Biological Research Center. We have used PCR analysis to identify homozygous mutant lines for all family members except AtBBE-like23, which appears to be embryonic lethal. We have determined phylogenetic relationships between AtBBE-like family genes. Because Atbbe28 mutants show reduced salt tolerance and biomass, and BBEs in other plants are upregulated in response to stress and pathogenic attack, leaves from Atbbe-like mutants grown in normal conditions as well as salt stress conditions were examined. Atbbe-like mutants showed significant changes in leaf area, leaf perimeter, leaf length, leaf width, and leaf length:width ratio compared to wild type when grown in soil and sterile conditions, in normal media and salt stress. There were also significant changes in pigment levels compared to wild type for chlorophyll a, chlorophyll b, and carotenoid levels. The relative expression levels of YABBY5 were decreased in some Atbbe-like mutants compared to wild type.
|Commitee:||Fowler, Thomas, Liebl, Faith|
|School:||Southern Illinois University at Edwardsville|
|School Location:||United States -- Illinois|
|Source:||MAI 58/06M(E), Masters Abstracts International|
|Subjects:||Molecular biology, Plant sciences|
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