Most plants and algae have a chloroplast genome containing over a hundred genes. We were one of the first labs to report an unusual genome organization in dinoflagellates, an important group of algae forming part of the coral-algal symbiosis and responsible for red tides. Dinoflagellates have lost most of their chloroplast genes to the nucleus, and the remainder are located on small plasmids, typically containing a single gene (1). Primary transcripts from the whole plasmid are processed in various ways (2), including the addition of a polyU tail. We are interested in understanding more about how the genome is maintained and transcribed. We are also keen to develop the chloroplast genome as a genetic marker for studies on coral bleaching (3) in which coral hosts expel their dinoflagellate symbionts.
An important group of protozoan parasites, the Apicomplexa (which include Toxoplasma and Plasmodium, and are a sister group to the dinoflagellates) contain a remnant chloroplast which contains a genome of 35 kbp (4, 5). The remnant chloroplast is essential for parasite survival, and we now know that some antimalarials, such as clindamycin, work by interfering with it. However, little is known about gene expression in the parasite chloroplast, how it is regulated, and how it is co-ordinated with expression of the nuclear genome. We aim to understand more about these important aspects of parasite biology,
Plants and algae have a novel protein, cytochrome c6A, which is related to the well-characterized cytochrome c6 that can transfer electrons from the cytochrome bf complex to Photosystem I in some algae. However, cytochrome c6A is unable to carry out this function because (among other reasons) its redox potential is unsuitable. Having discovered this protein, we want to find out what it does – it is highly conserved, suggesting an important function (6, 7).
There is increasing interest in algae as a renewable energy source. They do not require valuable agricultural land for cultivation (and could be grown offshore). They can also be used for treatment of waste water, and for scrubbing carbon dioxide from industrial flue gases. The lab is a member of the Algal Bioenergy Consortium, based in Cambridge and with collaborators elsewhere, and we aim to apply our expertise in algal biology to renewable energy generation.
1) Howe CJ, Nisbet RER, Barbrook AC (2008) "The remarkable chloroplast genome of dinoflagellates" Journal of Experimental Botany 59 1035-1045
2) Nisbet RER, Hiller RG, Barry ER, Skene P, Barbrook AC, Howe CJ (2008) "Transcript analysis of dinoflagellate plastid gene minicircles" Protist 159 31-39
3) Barbrook AC, Visram S, Douglas A, Howe CJ (2006) "Molecular diversity of dinoflagellate symbionts of Cnidaria: the psbA minicircle of Symbiodinium" Protist 157 159-171
4) Howe CJ (1992) "Plastid origin of an extrachromosomal DNA molecule from Plasmodium, the causative agent of malaria" Journal of Theoretical Biology 158 199-205
5) Barbrook AC, Howe CJ, Purton S (2006) "Why are plastid genomes retained in non-photosynthetic organisms?" Trends in Plant Science 11 101-108
6) Molina-Heredia FP, Wastl J, Navarro JA, Bendall DS, Hervas M, Howe CJ, De La Rosa MA (2003) "A new function for an old cytochrome" Nature 424 33-34
7) Worrall JAR, Schlarb-Ridley BG, Reda T, Marcaida MJ, Moorlen RJ, Wastl J, Hirst J, Bendall DS, Luisi BF, Howe CJ (2007) "Modulation of heme redox potential in the cytochrome c6 family" Journal of the American Chemical Society 129 9468-9475