EPSRC Network on Evolvability in Biology & Software Systems

Evolvability, Genetics & Development in Natural and Constructed Systems: Abstracts of the EPSRC Evolvability Network Symposium

Tewin Bury Farm Hotel, Hertfordshire, England, UK
26-28 August 2003


University of Hertfordshire Computer Science Technical Report 389
C. L. Nehaniv, P. J. Bentley & S. Kumar (Editors)

Cell Wall Development in Diatoms - The Challenge to Understanding Pattern Control in a Unicell

Cell Wall Development in Diatoms - The Challenge to Understanding Pattern Control in a Unicell

EILEEN J. COX

Department of Botany, The Natural History Museum, Cromwell Road, London, SW7 5BD
United Kingdom

E.J.Cox@nhm.ac.uk


Diatoms are renowned for the possession of symmetrical, regularly patterned, silica cell walls, whose beauty has fascinated microscopists for over 150 years. Yet the biological pathways determining that pattern remain obscure. Similarly, the interaction between genetics and environment remains poorly understood and in many cases even intrinsic morphological variability due to size reduction is undocumented. Yet the very diversity and regularity of wall structure offers a possibly unique opportunity to investigate the relationships between genetics, gene expression, cell biology and environment in the formation of an inorganic structure by a unicellular protist. This talk will review the current state of knowledge about the cell biology of diatom cell wall morphogenesis. The diversity of wall structure between diatom genera offers an opportunity to determine whether different cellular components are involved with the formation of different structures, while variability in degree of development or arrangement of homologous structures within genera would allow the fine control of pattern to be investigated. It will also seek to illustrate some of the intrinsic morphological variability within species and how the peculiarities of the diatom life cycle may be exploited to understand pattern setting and control. Some of the more interesting issues include polarity setting, colony formation or break-up, and environmentally induced morphological variation: 1. Diatoms may exhibit an inherent polar asymmetry that is set de novo after sexual reproduction, whereas others are structurally symmetrical, but facultatively heteropolar. 2. Some species may exhibit morphological variability in response to changes in environmental conditions, and occasionally this can be dramatically demonstrated by the occurrence in a single cell of valves that would normally be identified as separate species. 3. Although intrinsically unicellular, some diatoms can form colonies in which cells are normally linked by interlocking spines, but intermittently able to separate by changing the shape of the spines. 4. Others may alternate between a potentially motile life-style and a non-motile one by modifying wall morphology.