Edinburgh, Scotland, United Kingdom - TAIR

Assembly of the Cellulose Synthase Complex
occurs within a specialised compartment that
is derived from the endoplasmic reticulum
Cellulose is synthesised at the plasma membrane by a large multiprotein
complex termed the Cellulose Synthase Complex (CSC). In cells that undergo
deposition of a secondary cell wall, the CSC is assembled from three different
CesA subunits; CesA4, CesA7 and CesA8. Previous work has shown the CSC
to be found in the Golgi 1 and a small compartment that resides directly below the
sites of secondary wall synthesis. 2 We have recently developed a method to
visualise individual CSCs directly using Transmission Electron Microscopy. We
have observed CSCs to be arranged in a very large 3-dimensional array within
a membrane bound compartment. The identification of these CSC-containing
arrays is further supported from immunogold labelling and mutant analyses.
Characterisation of this compartment suggests that it is a specialised ER body
and is the likely location for the synthesis and assembly of the CSC. The results
have identified an entirely novel pathway for membrane protein trafficking in
which a membrane-bound protein is able to avoid co-translational insertion into
the ER membrane, instead passing through into the lumen of the ER. These
results have profound implications for protein trafficking in general, but in
particular for how the CSC assembles and functions at the plasma membrane.
1 Wightman, R., and Turner, S. R. (2008). The roles of the cytoskeleton during
cellulose deposition at the secondary cell wall. Plant J 54, 794-805.
2 Wightman, R., Marshall, R., and Turner, S. R. (2009). A cellulose synthasecontaining
compartment moves rapidly beneath sites of secondary wall synthesis.
Plant Cell Physiol 50, 584-594.
96
C45
Saturday 15:15 - 15:30
Bioenergy
Raymond Wightman
Aleksandr Mironov
Simon Turner
Faculty of Life Sciences
University of Manchester
UK