Causation and Consequences of Polyploidy in Cyanobacteria, Synechococcus sp. PCC 7002

Frank, Jillian

Undergraduate Honors Thesis

Causation and Consequences of Polyploidy in Cyanobacteria, Synechococcus sp. PCC 7002 Pubblico Deposited

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Citeable URL: https://scholar.colorado.edu/concern/undergraduate_honors_theses/pz50gx268

Abstract

The number of chromosome copies within an organism can directly impact gene expression, phenotype, and offspring viability. The presence of multiple copies of chromosomes, known as polyploidy, may confer additional consequences that remain unknown. It is important to understand the driving mechanisms behind chromosome replication so as to maintain the integrity of gene expression and inheritance of those genes and to avoid the retention of deleterious mutations. Currently, most model prokaryotic organisms are monoploid, therefore the effects of multiple chromosome copies in prokaryotes remains understudied as does the chromosome replication mechanisms for polyploid microbes. The cyanobacterium, Synechococcus sp. PCC 7002 is a strong candidate as a model organism particularly for use in synthetic biology and biofuel production based on its photosynthetic abilities. In this study, through CRISPR-interference gene knockdown of possible chromosome replication initiation factors as well as conferring heterogeneity of antibiotic resistance at a single, competing locus, we aim to elucidate both possible mechanisms and consequences of polyploidy in a potential model prokaryotic organism. We find that two conserved genes, priA and recG have no major phenotypic effect on ploidy level, and likely are not key regulators in chromosome replication. We also find that in the absence of selective pressure, there is random gene elimination to a homogenous allelic state, suggesting that heterogenetic polyploidy may not be a naturally occurring phenomenon or benefit in polyploid prokaryotes. Further investigation is required to confirm the definitive functions and significance of priA and recG in the chromosome replication pathway, as well as if gene elimination always occurs in a heterozygotic polyploid cyanobacteria in the absence of selection.

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