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The genome sequence of black cottonwood (Populus trichocarpa) reveals 18 conserved cellulose synthase (CesA) genes
KTH, School of Biotechnology (BIO).
KTH, School of Biotechnology (BIO).
KTH, School of Computer Science and Communication (CSC), Numerical Analysis and Computer Science, NADA.
KTH, School of Biotechnology (BIO).ORCID iD: 0000-0003-3281-8088
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2005 (English)In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 221, no 5, 739-746 p.Article in journal (Refereed) Published
Abstract [en]

The genome sequence of Populus trichocarpa was screened for genes encoding cellulose synthases by using full-length cDNA sequences and ESTs previously identified in the tissue specific cDNA libraries of other poplars. The data obtained revealed 18 distinct CesA gene sequences in P. trichocarpa. The identified genes were grouped in seven gene pairs, one group of three sequences and one single gene. Evidence from gene expression studies of hybrid aspen suggests that both copies of at least one pair, CesA3-1 and CesA3-2, are actively transcribed. No sequences corresponding to the gene pair, CesA6-1 and CesA6-2, were found in Arabidopsis or hybrid aspen, while one homologous gene has been identified in the rice genome and an active transcript in Populus tremuloides. A phylogenetic analysis suggests that the CesA genes previously associated with secondary cell wall synthesis originate from a single ancestor gene and group in three distinct subgroups. The newly identified copies of CesA genes in P. trichocarpa give rise to a number of new questions concerning the mechanism of cellulose synthesis in trees.

Place, publisher, year, edition, pages
2005. Vol. 221, no 5, 739-746 p.
Keyword [en]
Populus, paleopolyploids, cellulose synthase, gene duplication, paralogues
National Category
Industrial Biotechnology
Identifiers
URN: urn:nbn:se:kth:diva-6245DOI: 10.1007/s00425-005-1498-4ISI: 000230490200013Scopus ID: 2-s2.0-22444446783OAI: oai:DiVA.org:kth-6245DiVA: diva2:10901
Note
QC 20101001. Uppdaterad från In press till Published (20101001).Available from: 2005-09-13 Created: 2005-09-13 Last updated: 2010-10-21Bibliographically approved
In thesis
1. Cellulose synthases in Populus- identification, expression analyses and in vitro synthesis
Open this publication in new window or tab >>Cellulose synthases in Populus- identification, expression analyses and in vitro synthesis
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Cellulose is a biopolymer of great relevance in the plant cell walls, where it constitutes the most important skeletal component. Cellulose is also an important raw material in the pulp- and paper, forest, and textile industries, among others. Cellulose biosynthesis in particular, and xylogenesis in general are processes which are currently poorly understood. Yet, research in cellulose synthesis is progressing and different applications of cellulose, mainly cellulose derivatives for e.g. pharmaceuticals and coatings, are constantly emerging. This thesis depicts how cellulose synthase (CesA) genes in Populus were identified and characterized by gene expression- and bioinformatics analyses. Within an EST database of more than 100,000 clones from wood forming tissues of three different Populus taxa, ten CesA genes were identified in Populus tremula x tremuloides. Subsequent gene expression analyses by using microarrays and real-time PCR experiments in woody tissues, revealed distinct regulation patterns among the genes of interest. This enabled proper classification and characterization of the secondary cell wall related CesA genes, in particular. Bioinformatic analyses of the genome sequence of Populus trichocarpa further provided a complete picture of the number of putative CesA genes retained after several duplication events during tree evolution. In contrast to the previously reported set of ten 'true' CesA genes in many other plant species, the genome of P. trichocarpa encodes 18 putative proteins, which could be assembled into nine groups according to their sequence similarities. Interestingly, studies in the EST database suggested that paralogs within at least two groups have corresponding orthologs in P. tremula x tremuloides, which are furthermore transcribed. This implies that at least some of the duplicated genes have remained functional, or may have acquired a modified function.

By focusing on the CesA genes associated with secondary cell wall formation, cellulose synthesis was also studied in poplar cell suspension cultures. Selection of CesA enriched material was performed by determining expression intensities of the CesA genes using RT-PCR, whereupon membrane protein extraction was initiated. CesA proteins are part of large cellulose synthesizing complexes in the plasma membrane. Subsequent proteomic approaches comprised partial purification of these cellulose synthesizing complexes from protein enriched culture material and in vitro cellulose synthesis experiments. De novo synthesized material was successfully characterized and the acquired yields were as high as 50% cellulose (compared to previously reported yields of 30% in other plant systems) of the total in vitro synthesized product. Elevated CesA gene expression levels can thus be correlated to increased protein activity in poplar cell suspension cultures. In addition, antibodies raised against CesA antigens were used in Western blot analyses comprising samples along the protein extraction- and purification procedure. Proteins with corresponding molecular weight to the theoretical 120kDa of CesA proteins were recognized by a range of different specific antibodies. The study demonstrates that poplar cell suspension cultures can provide a valuable model system for studies of cellulose synthesis and different aspects of xylogenesis.

Place, publisher, year, edition, pages
Stockholm: KTH, 2005. 79 p.
Keyword
cellulose synthase, Populus, secondary cell wall, gene upregulation, cell suspension culture, stationary phase
National Category
Industrial Biotechnology
Identifiers
urn:nbn:se:kth:diva-414 (URN)91-7178-109-9 (ISBN)
Public defence
2005-09-23, Svedbergssalen, FD5, AlbaNova Universitetscentrum, Roslagstullsbacken 21, Stockholm, 10:00
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Note
QC 20101005Available from: 2005-09-13 Created: 2005-09-13 Last updated: 2010-10-05Bibliographically approved

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