Functional genomics of the unicellular cyanobacterium Synechococcus elongatus PCC 7942

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Title: Functional genomics of the unicellular cyanobacterium Synechococcus elongatus PCC 7942
Author: Chen, You
Abstract: Unicellular freshwater cyanobacterium Synechococcus elongatus PCC 7942 is the model organism for studying the circadian clock in cyanobacteria . Despite tremendous work over the last decade in identification of clock -related loci and elucidation of molecular mechanisms of the central oscillator , many details of the basic steps in generating circadian rhythms of biological processes remain unsolved and many components are still missing . A transposon -mediated mutagenesis and sequencing strategy has been adopted to disrupt essentially every locus in the genome so as to identify all of the loci that are involved in clock function . The complete genome sequence has been determined by a combination of shotgun sequences and transposon -mediated sequences . The S . elongatus PCC 7942 genome is 2 ,695 ,903 bp in length , and has a 55 .5 % GC content . Automated annotation identified 2 ,856 protein -coding genes and 51 RNA coding loci . A system for community refinement of the annotation was established . Organization and characteristic features of the genome are discussed in this dissertation . More than 95 % of the PCC 7942 genome has been mutagenized and mutants affected in approximately 30 % of loci have been screened for defects in circadian function . Approximately 70 new clock loci that belong to different functional categories have been discovered through a team effort . Additionally , functional analysis of insertion mutants revealed that the Type -IV pilus assembly protein PilN and the RNA chaperon Hfq are involved in transformation competence of S . elongatus cells . Functional analysis of an atypical short period kaiA insertional mutant showed that the short period phenotype is caused mainly by the truncation of KaiA by three amino acid residues . The interaction between KaiC and the truncated KaiA is weakened as shown by fluorescence anisotropy analysis . Deletion analysis of pANL , the large endogenous plasmid , implies that two toxin -antitoxin cassettes were responsible for inability to cure cells of this plasmid . In summary , the results indicate that this functional genomics project is very promising toward fulfilling our goal to assemble a comprehensive view of the cyanobacterial circadian clock . The mutagenesis reagents and dataset generated in this project will also benefit the greater scientific community .
URI: http : / /hdl .handle .net /1969 .1 /ETD -TAMU -1552
Date: 2009-05-15

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Functional genomics of the unicellular cyanobacterium Synechococcus elongatus PCC 7942. Available electronically from http : / /hdl .handle .net /1969 .1 /ETD -TAMU -1552 .

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