Genetic and Chemical Diversity of Mycosporine-Like Amino Acids and Glycosylated Variants in Cyanobacteria

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Title: Genetic and Chemical Diversity of Mycosporine-Like Amino Acids and Glycosylated Variants in Cyanobacteria
Author: Arsin, Sila
Other contributor: Helsingin yliopisto, Maatalous-metsätieteellinen tiedekunta
University of Helsinki, Faculty of Agriculture and Forestry
Helsingfors universitet, Agrikultur- och forstvetenskapliga fakulteten
Publisher: Helsingin yliopisto
Date: 2019
Language: eng
Thesis level: master's thesis
Degree program: Mikrobiologian ja mikrobibiotekniikan maisteriohjelma
Master's Programme in Microbiology and Microbial Biotechnology
Magisterprogrammet i mikrobiologi och mikrobibioteknik
Specialisation: ei opintosuuntaa
no specialization
ingen studieinriktning
Abstract: Mycosporines and mycosporine-like amino acids (MAAs) are small-molecules that provide UV protection in a broad range of organisms. Cyanobacteria produce a diverse set of MAA chemical variants, many of which are glycosylated. Even though the biosynthetic pathway for the production of a common cyanobacterial MAA, shinorine, is known, the biosynthetic origins of the glycosylated variants remains unclear. In this work, bioinformatics analyses were performed to catalogue the genetic diversity encoded in the MAA gene clusters in cyanobacterial genomes and identify a set of enzymes that might be involved in MAA biosynthesis. A total of 211 cyanobacterial genomes were found to contain the MAA gene cluster, with six containing glycosyltransferase genes within the gene cluster. Afterwards, 38 strains from the University of Helsinki Culture Collection were tested for the production of MAAs using QTOF-LC/MS analyses. This resulted in the identification of several novel glycosylated MAA chemical variants from Nostoc sp. UHCC 0302, which contained a 7.4 kb MAA biosynthetic gene cluster consisting of 7 genes, including two for glycosyltransferases and one for dioxygenase. Heterologous expression of this gene cluster in Escherichia coli TOP10 resulted in the production of a glycosylated porphyra-334 variant of 509 m/z by the transformant cells, showing that colanic acid biosynthesis glycosyltransferases can catalyse the addition of hexose to MAAs. These results suggested a biosynthetic route for the production of glycosylated MAAs in cyanobacteria and allowed to propose a putative role for dioxygenases in MAA biosynthesis. Further characterization of additional glycosyltransferases is necessary to improve our understanding of glycosylated MAA biosynthesis and functionality, which could be applied to large scale processes and be used in industrial applications.
Subject: cyanobacteria
genome mining
mass spectrometry
liquid chromatography
heterologous expression
mycosporine-like amino acids

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