Plant Cell Biology

Welcome and Introduction to Plant Cell Biology

This is a young department, established in 1992. Our goal is to increase understanding of how cells control their use of energy in photosynthesis and respiration, how protein structure may be modified as part of this control, and how (and why) the genes that encode the proteins of photosynthesis and respiration might be switched on and off. We work with plant cells, chloroplasts, mitochondria, photosynthetic bacteria, and with isolated proteins, genes, and membrane systems. Current research topics, broadly defined, are as follows.

1. Redox control of gene expression.

Chloroplasts and mitochondria are descendants of bacteria, from which they retain genes for a small but constant sub-set of their own components. We suspect that they may also have inherited bacterial redox control systems to regulate these genes. This hypothesis is currently being tested. Krassimir Alexciev, Carol Allen, John Allen, Martha Escobar, Thomas Pfannschmidt, Gunilla Håkansson, Anna Tullberg.

2. The structural basis of regulation by protein phosphorylation.

The structural changes of light-harvesting complexes during regulation are sought by a combination of high-resolution structural studies and directed mutation to alter specific structural features such as sites of modification. By NMR (in collaboration with Physical Chemistry 2) Dalibor Stys has shown the existence of a structure unique to the phosphorylated form of the N-terminal LHC II peptide. Anders Nilsson has recently obtained IR and CD spectra showing that phosphorylation is accompanied by helix formation. These results support the "molecular recognition" view of regulation of photosynthesis by protein phosphorylation. Krassimir Alexciev, John Allen, Jens Forsberg, Anders Nilsson.

3. Redox control of thylakoid, chromatophore and mitochondrial protein kinases.

We have recently found that all 13 chloroplast thylakoid phosphoproteins observed by phosphoimaging are controlled by a single sensor with Em = 50 mV, n = 1, with two of them showing reverse redox dependency (perversely phosphorylated under oxidising conditions). Similar redox-dependent protein phosphorylation is seen in mitochondria. John Allen, Gunilla Håkansson, André Struglics, Anna Tullberg.

4. Time-resolved imaging spectroscopy.

Time-resolved imaging spectroscopy is used as a non-invasive probe, by rapid computer acquistion of digitized images of chlorophyll fluorescence. Variations in fluorescence can then be measured simultaneously in a large population of cells. Thus subtle, adaptive responses can be used for the first time as genetic markers in screening for mutation impairing adaptations. Krassimir Alexciev, John Allen, Paul Davison.

5. In vitro culture and transformations.

Genetic transformation is carried out using particle bombardment and Agrobacterium tumefasciens. Vectors are made with antisense constructs in order to study protein function, including heat-shock proteins and molecular chaperones. Using cell fusion and gene transfer, new possibilities are created for fundamental studies of gene regulation and recombination. Anna Collén, Carin Jarl- Sunesson.

Additionally, we have fluorescence spectroscopy (Perkin Elmer) and induction (Walz PAM) apparatus, and flash kinetic spectroscopy (Glynn Research). We share a phosphoimager (Molecular Dynamics) and automated DNA sequencer (Perkin Elmer). We also have our own molecular graphics workstation (Silicon Graphics) in addition to a network of Macintosh computers and PCs.

Excellence is on the agenda!

John F. Allen
Professor of Plant Cell Biology