The
reaction of an end-on Cr­(III)-superoxo complex bearing a 14-membered
tetraazamacrocyclic TMC ligand, [CrIII(14-TMC)­(O2)­(Cl)]+, with nitric oxide (NO) resulted in the generation
of a stable Cr­(IV)-oxo species, [CrIV(14-TMC)­(O)­(Cl)]+, via the formation of a Cr­(III)-peroxynitrite intermediate
and homolytic O–O bond cleavage of the peroxynitrite ligand.
Evidence for the latter comes from electron paramagnetic resonance
spectroscopy, computational chemistry and the observation of phenol
nitration chemistry. The Cr­(IV)-oxo complex does not react with nitrogen
dioxide (NO2), but reacts with NO to afford a Cr­(III)-nitrito
complex, [CrIII(14-TMC)­(NO2)­(Cl)]+. The Cr­(IV)-oxo and Cr­(III)-nitrito complexes were also characterized
spectroscopically and/or structurally

Ares, Manuel

Bachy, Charles

Simmons, Melinda P

Sudek, Lisa

Sudek, Sebastian

van Baren, Marijke J

Worden, Alexandra Z

Molecular Biology and Evolution

PubMed

Spliceosomal introns are a hallmark of eukaryotic genes that are hypothesized to play important roles in genome evolution but have poorly understood origins. Although most introns lack sequence homology to each other, new families of spliceosomal introns that are repeated hundreds of times in individual genomes have recently been discovered in a few organisms. The prevalence and conservation of these introner elements (IEs) or introner-like elements in other taxa, as well as their evolutionary relationships to regular spliceosomal introns, are still unknown. Here, we systematically investigate introns in the widespread marine green alga Micromonas and report new families of IEs, numerous intron presence-absence polymorphisms, and potential intron insertion hot-spots. The new families enabled identification of conserved IE secondary structure features and establishment of a novel general model for repetitive intron proliferation across genomes. Despite shared secondary structure, the IE families from each Micromonas lineage bear no obvious sequence similarity to those in the other lineages, suggesting that their appearance is intimately linked with the process of speciation. Two of the new IE families come from an Arctic culture (Micromonas Clade E2) isolated from a polar region where abundance of this alga is increasing due to climate induced changes. The same two families were detected in metagenomic data from Antarctica--a system where Micromonas has never before been reported. Strikingly high identity between the Arctic isolate and Antarctic coding sequences that flank the IEs suggests connectivity between populations in the two polar systems that we postulate occurs through deep-sea currents. Recovery of Clade E2 sequences in North Atlantic Deep Waters beneath the Gulf Stream supports this hypothesis. Our research illuminates the dynamic relationships between an unusual class of repetitive introns, genome evolution, speciation, and global distribution of this sentinel marine alga

eScholarship - University of California

Intron Invasions Trace Algal Speciation and Reveal Nearly Identical Arctic and Antarctic Micromonas Populations

Spliceosomal introns are a hallmark of eukaryotic genes that are hypothesized to play important roles in genome evolution but have poorly understood origins. Although most introns lack sequence homology to each other, new families of spliceosomal introns that are repeated hundreds of times in individual genomes have recently been discovered in a few organisms. The prevalence and conservation of these introner elements (IEs) or introner-like elements in other taxa, as well as their evolutionary relationships to regular spliceosomal introns, are still unknown. Here, we systematically investigate introns in the widespread marine green alga Micromonas and report new families of IEs, numerous intron presence-absence polymorphisms, and potential intron insertion hot-spots. The new families enabled identification of conserved IE secondary structure features and establishment of a novel general model for repetitive intron proliferation across genomes. Despite shared secondary structure, the IE families from each Micromonas lineage bear no obvious sequence similarity to those in the other lineages, suggesting that their appearance is intimately linked with the process of speciation. Two of the new IE families come from an Arctic culture (Micromonas Clade E2) isolated from a polar region where abundance of this alga is increasing due to climate induced changes. The same two families were detected in metagenomic data from Antarctica-a system where Micromonas has never before been reported. Strikingly high identity between the Arctic isolate and Antarctic coding sequences that flank the IEs suggests connectivity between populations in the two polar systems that we postulate occurs through deep-sea currents. Recovery of Clade E2 sequences in North Atlantic Deep Waters beneath the Gulf Stream supports this hypothesis. Our research illuminates the dynamic relationships between an unusual class of repetitive introns, genome evolution, speciation, and global distribution of this sentinel marine alga. © 2015 The Author

Simmons, Melinda P.

Van Baren, Marijke J.

Worden, Alexandra Z.

OceanRep

Intron invasions trace algal speciation and reveal nearly identical arctic and antarctic micromonas populations

Melinda P. Simmons

Charles Bachy

Sebastian Sudek

Marijke J. van Baren

Lisa Sudek

Manuel Ares

Alexandra Z. Worden

Crossref

Intron Invasions Trace Algal Speciation and Reveal Nearly Identical Arctic and AntarcticMicromonasPopulations

Atsutoshi Yokoyama (1901038)

Kyung-Bin Cho (1271760)

Kenneth D. Karlin (1326828)

Wonwoo Nam (1289187)

FigShare