Cloning and characterization of genes involved in carbohydrate metabolism in the marine red alga Gracilaria gracilis

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dc.contributor.authorLluisma, A.O.
dc.date.accessioned2007-11-13
dc.date.available1997-04-01en
dc.date.available2007-11-13
dc.date.issued1997
dc.description.abstractThe molecular biology of carbohydrate metabolism in red algae is poorly known. Enzymological studies are few, and no gene for the biosynthesis of sugar nucleotides and polysaccharides has so far been characterized. To isolate genes involved in carbohydrate metabolism in Gracilaria gracilis, genomic libraries were screened with homologous probes prepared either by PCR with degenerate primers, or from cDNAs previously isolated for generating expressed sequence tags (ESTs) from G. gracilis. Genes involved in carbohydrate metabolism, photosynthesis, protein synthesis and degradation, amino acid metabolism, and stress response were among those tagged by the ESTs. Three genes were characterized. These encode galactose-1-phosphate uridylyltransferase (GALT, named GgGALT1), a key enzyme for scD-galactose metabolism; UDPglucose pyrophosphorylase (UGPase; GgUGP), a key enzyme for sugar nucleotide synthesis; and starch branching enzyme (SBE; GgSBE1), which helps determine the structure of floridean starch. The three genes are devoid of introns. Each possesses a polyadenylation signal, TAAA, which occurs in all G. gracilis genes so far characterized, as well as a potential TATA box. Southern hybridization experiments indicate that the three genes are single-copy, but that other genes related to GgGALT1 and GgSBE1 exist. GgGALT1 and GgUGP are each located close to another gene, hinting that occurrence of closely-spaced genes, atypical in eukaryotic genomes, may not be uncommon in the G. gracilis genome. The deduced proteins show high sequence similarity with their homologs in other organisms, but intriguing differences, such as nonconservative substitutions at functionally important sites, were observed. The protein encoded by GgSBE1 lacks an N-terminal portion that could contain a possible target peptide, consistent with the cytosolic localization of floridean starch synthesis. The GgUGP and GgSBE1 proteins are as phylogenetically related to plant as they are to their animal and fungal homologs.en
dc.description.degreeDoctor of Philosophy
dc.formatTexten
dc.format.extent1 digital file (123 p. : ill.)en
dc.format.mimetypeApplication/pdf
dc.identifier.urihttp://hdl.handle.net/10625/16331
dc.identifier.urihttp://hdl.handle.net/10222/55490
dc.language.isoen
dc.publisherDalhousie University, Halifax, NS, CAen
dc.subjectALGAEen
dc.subjectGENETIC IMPROVEMENTen
dc.subjectGENESen
dc.subjectBIOLOGICAL CONTROLen
dc.subjectCHEMICAL ANALYSISen
dc.titleCloning and characterization of genes involved in carbohydrate metabolism in the marine red alga Gracilaria gracilisen
dc.typeThesisen
idrc.dspace.accessIDRC Onlyen
idrc.project.number910143
idrc.project.titleSeaweeds and Invertebrates (Philippines)en
idrc.rims.adhocgroupIDRC SUPPORTEDen

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