Regulation of microbial sunscreen biosynthesis

Regulation of microbial sunscreen biosynthesis Regulation of microbial sunscreen biosynthesis Some microorganisms, notably cyanobacteria, are known to synthesize secondary metabolites that serve a sunscreen function to protect them from damaging effects of exposure to ultraviolet radiation (UV). In cyanobacteria, two main types of such compounds have been described: scytonemin, a unique alkaloid of interesting biological properties, and mycosporine-like amino acids (MAAs), a family of small water-soluble compounds structurally based on the condensation of amino acid residues on a cyclohexenone ring. In the past few years we have successfully developed the cyanobacterial strain, Nostoc punctiforme ATCC 29133, to study the genetic and molecular basis of scytonemin and MAA biosynthesis and regulation. Great strides have been made during the past few years in this field of research regarding the molecular genetic basis of microbial sunscreens. We propose here to bring this research to the next level, by probing aspects of sunscreen biology relating to the association of gene function with cell compartmentalization, relating to their regulation and their evolution. This work will provide links between existing knowledge at the molecular, physiological and environmental levels of organization, eventually enabling a systems understanding of microbial sunscreens. We plan to test the function of genes predicted to be responsible for the late steps in scytonemin biosynthesis, and to study their targeting to the periplasm, en route to an eventual excretion of the final product. We will probe aspects of genetic regulation as a response to exposure to UV by establishing gene expression patterns and transcriptional units in the mycosporine locus and by testing the role of conserved two-component regulators associated with the scytonemin operon. Finally we will study the evolutionary aspects of the sunscreen loci, in an attempt to trace the phylogenetic origins of this adaptations among microorganisms and how they might be a reflect trends in UV exposure during Earths history. To reach our goals we will deploy a range of techniques ranging from the engineering and phenotypic characterization of Nostoc knock-out mutants, to the use of fusion constructs with GFP coupled to confocal imaging, to transcriptome characterization with genomic microarrays