Biology subjects

Nisbet, R. E. R.

Publications and source records attributed to Nisbet, R. E. R..

5 recordsLinked to original sources

bioRxiv2025

Bioelectricity generation by Symbiodinium microadriaticum: a symbiont-forming photosynthetic dinoflagellate alga from coral reefs

Climate change is intensifying the phenomenon of coral bleaching, a highly ecologically damaging process that stems from the breakdown in the symbiotic relationship between photosynthetic dinoflagellate algae and Cnidaria (animals). Currently, little is understood about bleaching at the molecular level, since changes in metabolic and redox interactions between the dinoflagellate algae and Cnidaria are challenging to study. Here, we developed electrochemical approaches to measure extracellular electron transfer (EET, a type of bioelectricity) in Symbiodinium microadriaticum, a model species of symbiont-forming dinoflagellate algae, and show how this can be used to assess intracellular bioenergetic fluctuations within the alga. We show that EET is dependent on two major intracellular pathways - photosynthesis and respiration - and reveal that expelled electrons exit the cell via diffusible electron carriers. We confirm that EET activity can be affected by environmental stressors linked to coral bleaching, such as changes in temperature, pH and light intensity. Overall, this is a direct and non-invasive approach to provide quantitative measurements of S. microadriaticums bioenergetics and redox exchanges with the environment in stress conditions. This platform can aid our understanding of the coral-dinoflagellate symbiosis and the molecular mechanisms of bleaching.

microbiology↗

bioRxiv2021

The evolution of the cytochrome c6 family of photosynthetic electron transfer proteins

During photosynthesis, electrons are transferred between the cytochrome b6f complex and photosystem I. This is carried out by the protein plastocyanin in plant chloroplasts. In contrast, electron transfer can be carried out by either plastocyanin or cytochrome c6 in many cyanobacteria and eukaryotic algal species. There are three further cytochrome c6 homologues: cytochrome c6A in plants and green algae, and cytochromes c6B and c6C in cyanobacteria. The function of these proteins is unknown. Here, we present a comprehensive analysis of the evolutionary relationship between the members of the cytochrome c6 family in photosynthetic organisms. Our phylogenetic analyses show that cytochrome c6B and cytochrome c6C are likely to be orthologues that arose from a duplication of cytochrome c6, but that there is no evidence for separate origins for cytochrome c6B and c6C. We therefore propose re-naming cytochrome c6C as cytochrome c6B. We show that cytochrome c6A is likely to have arisen from cytochrome c6B rather than by an independent duplication of cytochrome c6, and present evidence for an independent origin of a protein with some of the features of cytochrome c6A in peridinin dinoflagellates. We conclude with a new comprehensive model of the evolution of the cytochrome c6 family which is an integral part of understanding the function of the enigmatic cytochrome c6 homologues.

evolutionary biology↗

bioRxiv2019

Genetic tool development in marine protists: Emerging model organisms for experimental cell biology

Diverse microbial ecosystems underpin life in the sea. Among these microbes are many unicellular eukaryotes that span the diversity of the eukaryotic tree of life. However, genetic tractability has been limited to a few species, which do not represent eukaryotic diversity or environmentally relevant taxa. Here, we report on the development of genetic tools in a range of protists primarily from marine environments. We present evidence for foreign DNA delivery and expression in 13 species never before transformed and advancement of tools for 8 other species, as well as potential reasons for why transformation of yet another 17 species tested was not achieved. Our resource in genetic manipulation will provide insights into the ancestral eukaryotic lifeforms, general eukaryote cell biology, protein diversification and the evolution of cellular pathways.

ecology↗

bioRxiv2018

Genetic transformation of the dinoflagellate chloroplast

Coral reefs are some of the most important and ecologically diverse marine environments. At the base of the reef ecosystem are dinoflagellate algae, living in symbiosis with coral. Efforts to understand the relationship between alga and coral have been greatly hampered by the lack of an appropriate dinoflagellate genetic transformation technology. By making use of the plasmid-like fragmented chloroplast genome, we have introduced novel genetic material into the dinoflagellate chloroplast genome. We have shown that the introduced genes are expressed and confer the expected phenotypes. Genetically modified cultures have been grown for five months with subculturing, maintaining the introduced genes and phenotypes. This indicates that cells continue to divide after transformation and that the transformation is stable.

genetics↗

bioRxiv2018

A Pentatricopeptide Repeat Protein in the Plasmodium apicoplast is essential and shows sequence-specific RNA binding

The malaria parasite Plasmodium and other apicomplexans such as Toxoplasma evolved from photosynthetic organisms and contain an essential, remnant plastid termed the apicoplast. Transcription of the apicoplast genome is polycistronic with extensive RNA processing. Little is known about the mechanism of post-transcriptional processing. In plant chloroplasts, post-transcriptional RNA processing is controlled by multiple pentatricopeptide repeat (PPR) proteins. Here, we present the biochemical characterisation of the single apicoplast-targeted PPR protein. Apicoplast PPR1 is essential, and binds specific RNA sequences corresponding with previously characterized RNA processing sites. We identify the specific binding motif of PPR1. In RNAse protection assays, PPR1 shields apicoplast transcripts from ribonuclease degradation. Our results show that apicoplast RNA processing is under the control of a single protein, thus presenting an Achilles heel for the development of new anti-malarial drugs.

microbiology↗