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Tanya Soule




Cyanobacteria are photosynthesizing organisms that live in environments open to solar ultraviolet radiation. In order to survive in these environments, some cyanobacteria produce sunscreen pigments that convey the ability to tolerate harmful solar energy. The indole-alkaloid scytonemin is a sunscreen pigment that is widely produced among cyanobacteria. This sunscreen pigment intercepts photons before they can harm cellular machinery and DNA. The specific aim of this project is to determine if genes associated with scytonemin biosynthesis are expressed in response to environmental conditions. The genomic region associated with scytonemin biosynthesis is composed of a two-component regulatory system located immediately upstream from a 18-gene cluster that is cooperatively expressed in response to UVA as a metabolic network dedicated to scytonemin biosynthesis. To assess scytonemin response, cells were acclimated and grown under white light for one week and then subjected to the following environmental stresses for two days: UVA, UVB, high light, and oxidative stress. The presence of scytonemin was determined by absorbance measurement of acetone extraction. To determine transcript abundance, cDNA was measured using qPCR using primers targeting scytonemin biosynthetic genes, scyA, trpB, and Npun_F5233 and compared to control transcript levels for cells under white light only. Of the environmental conditions tested, scytonemin genes were upregulated, but scytonemin was induced and detected only in the UVA and UVB environmental conditions.



Expression of Genes Associated with Sunscreen Biosynthesis in the Cyanobacterium Nostoc Puntiforme

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