Poster: Cell walls

Abs # 624: Investigating the organization and function of the cellulose-synthesizing terminal complex using Physcomitrella patens

Presenter:	Roberts, Alison W, aroberts@uri.edu
Authors	Roberts, Alison W (A)   Bushoven, John  (A)   Roberts, Eric  (B)   Goss, Chessa  (A)
Affiliations:	(A): University of Rhode Island (B): Roger Williams University

Cellulose is synthesized at the plasma membrane as microfibrils that vary in diameter from about 3 nm in land plants to 25 nm in some algae. Microfibril structure is determined largely by the organization of arrays of integral plasma membrane protein particles known as ‘terminal complexes’. These terminal complexes contain the catalytic subunits of cellulose synthase encoded by a family of genes designated CesA. Although the CesA gene products of plants and bacteria share conserved regions, their extensive differences may contribute to variation in terminal complex and microfibril structure. We are examining the genetic basis for this variation by comparing the CesA genes of algae in which terminal complex structure ranges from rosettes to linear. In preparation for direct testing of the functions of domains potentially involved in terminal complex assembly, we are sequencing CesA genes from Physcomitrella patens, which is uniquely suited for targeted transformation and analysis of terminal complex structure by freeze fracture electron microscopy. Degenerate primers were used to amplify and clone fragments of 5 CesA genes from P. patens genomic DNA. Probes derived from the cloned fragments were used to isolate CesA clones from cDNA, genomic and BAC libraries from P. patens. CesA clones identified in EST libraries were also sequenced. A phylogenetic analysis of the P. patens CesA gene family will be presented. We gratefully acknowledge gifts of cDNA, genomic and BAC libraries from the University of Leeds, and EST clones from the University of Leeds and RIKEN Biological Resources Center. This work was funded by the U.S. Department of Agriculture NRI-GCP and the University of Rhode Island Foundation.