Algal Cell Biology
We aim to understand how environmental signals are perceived and interpreted in plant and algal cells. We are especially interested in how signals that are involved in responses to environmental factors interact with those that are involved in regulating development. The marine brown alga Fucus provides anideal model to study these processes. Fertilized eggs (zygotes) Polarize and divide into two unequal cells (rhizoid and thallus) that have different developmental fates.
We study of the role of cytoplasmic calcium as a signal both in the regulation of polarised growth of the rhizoid cell and in response to environmental perturbations that cause changes in cell volume. Calcium can be visualised by confocal imaging of fluorescent indicators by confocal imaging of flourescent indicators.
We are also studying the ion channels that regulate calcium movements across the cell membrane using patch clamp electrophysiology. Some of these channels can be activated by mechanical distortion of the membrane and may act as primary sensors of cell volume. We have used laser microsurgery to dissect single cells to gain access to the plasma membrane for patch clamp recording. We are also studying the responses of Fucus embryos to other stresses. Of particular importance is oxidative stress which occurs in response to a variety of environmental changes. The production of reactive oxygen species (ROS) appears to be tightly linked with the generation of calcium signals and our recent evidence suggests that both calcium and ROS have roles as intracellular signals with specific downstream responses
Cell fate determination and the control of development.
The pattern of development in plants and multicellular algae is dictated by the differentiation and division of cell types in various positions in the embryo and growing (meristematic) regions. We are particularly interested in the factors that regulate the developmental fate of cells in the embryo. It is known that the actin cytoskeleton plays a key role in establishing the polar axis along which apical-basal polarity is established. Our recent work has also shown a role for microtubules in the cell cortex in polarization. Dramatic reorganization of the microtubules occurs during polarization and the first cell division of the zygote. Using a combination of laser microsurgery and microinjection we have shown that the external cell wall is fundamental to determining and maintaining the fate of a particular cell type. In the multicellular embryo interactions between neighbouring cells and tissues are involved in determining the fate of particular cell types.
The Fucus zygote and embryo offers an excellent system for studying the molecular and cellular control of the cell cycle. In collaboration with Drs. F-Y Bouget and F. Corellou Observatoire Oceanologique, Banuyuls, Sur Mer, France we have been studying the co-ordination of cell cycle progression with the development of polarity. We have shown the presence of distinct checkpoints in the regulation of the cell cycle and a dependence of polarization on early cell cycle progression. This work has now progressed to investigate the role of calcium in the regulation of the cell cycle. This project is funded by the BBSRC in collaboration with Prof A.M.; Hetherington and Dr. M.R. McAInsh University of Lancaster. We are applying a combination of molecular and microscopic techniques, including multiphoton microscopy.
Motiliy and adhesion
Signalling during chemotaxis and settlement in Ulva zoospores.
Spores of the common green seaweed Ulva (formerly Enteromorpha)
intestinalis are know to be attracted to chemical signals released by
marine bacteria in biofilms. In collaboration with Drs. Ian Joint and
Karen Tait Plymouth Marine Laboratory,
funded by the Leverhulme
Trust Dr. Glen Wheeler is investigating the intracellular signalling
systems that underlie this response. The work is using a combination
of electrophysiological, and imaging techniques. In a related project
Stephanie Thompson (BBSRC CASE student with Prof. J.A. Callow, and Dr.
M.E. Callow, University
of Birmingham
has begun to investigate the cell biology of spore settlement and metamorphosis.
Motile responses of benthic diatoms to light gradients
Diatoms that inhabit the sediment in tidal estuaries are able to adjust
their position in the sediment to make effective use of available light
for photosynthesis. They do this by “gliding” along the
substratum in response to the light. Deidre MacLaughlan (PhD student,
University of Essex) has been studying whether certain species are able
to sense the direction and intensity of
the light. This work is also studying the intracellular
signaling systems that allow diatoms to change direction when the light
conditions suddenly change.
