当前位置： SCI文献检索 > Frontiers in Microbiology期刊下所有文献 > Mutational Studies of Putative Biosynthetic Genes for the Cyanobacterial Sunscreen Scytonemin in Nostoc punctiforme ATCC 29133.

Mutational Studies of Putative Biosynthetic Genes for the Cyanobacterial Sunscreen Scytonemin in Nostoc punctiforme ATCC 29133.

Abstract：

:The heterocyclic indole-alkaloid scytonemin is a sunscreen found exclusively among cyanobacteria. An 18-gene cluster is responsible for scytonemin production in Nostoc punctiforme ATCC 29133. The upstream genes scyABCDEF in the cluster are proposed to be responsible for scytonemin biosynthesis from aromatic amino acid substrates. In vitro studies of ScyA, ScyB, and ScyC proved that these enzymes indeed catalyze initial pathway reactions. Here we characterize the role of ScyD, ScyE, and ScyF, which were logically predicted to be responsible for late biosynthetic steps, in the biological context of N. punctiforme. In-frame deletion mutants of each were constructed (ΔscyD, ΔscyE, and ΔscyF) and their phenotypes studied. Expectedly, ΔscyE presents a scytoneminless phenotype, but no accumulation of the predicted intermediaries. Surprisingly, ΔscyD retains scytonemin production, implying that it is not required for biosynthesis. Indeed, scyD presents an interesting evolutionary paradox: it likely originated in a duplication event from scyE, and unlike other genes in the operon, it has not been subjected to purifying selection. This would suggest that it is a pseudogene, and yet scyD is highly conserved in the scytonemin operon of cyanobacteria. ΔscyF also retains scytonemin production, albeit exhibiting a reduction of the production yield compared with the wild-type. This indicates that ScyF is not essential but may play an adjuvant role for scytonemin synthesis. Altogether, our findings suggest that these downstream genes are not responsible, as expected, for the late steps of scytonemin synthesis and we must look for those functions elsewhere. These findings are particularly important for biotechnological production of this sunscreen through heterologous expression of its genes in more tractable organisms.

journal_name

Front Microbiol

journal_title

Frontiers in microbiology

authors

Ferreira D,Garcia-Pichel F

doi

10.3389/fmicb.2016.00735

subject

Has Abstract

pub_date

2016-05-18 00:00:00

pages

735

issn

1664-302X

journal_volume

pub_type

杂志文章

在线工具

Mutational Studies of Putative Biosynthetic Genes for the Cyanobacterial Sunscreen Scytonemin in Nostoc punctiforme ATCC 29133.