To gain a more complete picture of thylakoid membrane dynamics, it will be necessary to add fluorescent tags to those membrane proteins that are not naturally fluorescent. Unfortunately, GFP gene-fusions appear not to work in Synechococcus 7942 (Susan Golden, Texas A&M University, personal communication). However, GFP can be successfully expressed in other cyanobacteria, and mutant forms are available whose fluorescence excitation and emission does not overlap severely with that of the photosynthetic pigments (Spence et al., 2003).
There is scope for considerable further work on the dynamics of thylakoid membranes in green plants and green algae. Although it will not be possible to obtain quantitative diffusion coefficients for membrane components in stacked, laterally heterogeneous thylakoid membrane systems, it will be possible to see if there is an exchange of fluorescently tagged proteins between the grana and stroma lamellae, for example. This should give some fascinating insights into membrane biogenesis, electron transport, and the Photosystem II repair cycle.
Acknowledgements
CWM thanks Mary Sarcina and Mark Tobin for their essential contributions to the development of the technique, and Sarah Joshua and Caroline Aspinwall for generating the data used in Fig. 1. Work in the author’s laboratory is funded by BBSRC and the Wellcome Trust.
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