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Identification and expression analysis of genes encoding putative cellulose synthases (CesA) in the hybrid aspen, Populus tremula (L.) × P. tremuloides (Michx.)
KTH, Superseded Departments, Biotechnology.
KTH, Superseded Departments, Biotechnology.ORCID iD: 0000-0002-8576-4370
KTH, Superseded Departments, Biotechnology.ORCID iD: 0000-0002-4657-8532
KTH, Superseded Departments, Biotechnology.
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2004 (English)In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 11, no 3-4, 301-312 p.Article in journal (Refereed) Published
Abstract [en]

Cellulose is synthesized in plant cell walls by large membrane-bound protein complexes proposed to contain several copies of the catalytic subunit of the cellulose synthase, CesA. Here we report identification of 10 distinct CesA genes within a database of 100,000 ESTs of the hybrid aspen, Populus tremula (L.) x P. tremuloides (Michx.). Expression analyses in normal wood undergoing xylogenesis and in tension wood indicate xylem specific expression of four putative CesA isoenzymes, PttCesA1, PttCesA3-1, PttCesA3-2 and PttCesA9. Both the protein sequences and the expression profiles of PttCesA3-1 and PttCesA3-2 are very similar, and they may thus represent redundant copies of an enzyme with essentially the same function. Further, one of the generally more constitutively expressed CesA genes, PttCesA2, seems to be activated on the opposite side of a tension wood induced stem, while PttCesA6 appears to be more specific for leaf tissues. The rest of the hybrid aspen CesA genes were found to be relatively evenly expressed over the poplar tissues hereby studied.

Place, publisher, year, edition, pages
2004. Vol. 11, no 3-4, 301-312 p.
Keyword [en]
cellulose synthesis, expression profiling, hybrid aspen, plant cell wall, tension wood
National Category
Industrial Biotechnology
Identifiers
URN: urn:nbn:se:kth:diva-6244DOI: 10.1023/B:CELL.0000046408.84510.06ISI: 000225573000004OAI: oai:DiVA.org:kth-6244DiVA: diva2:10900
Note
QC 20100916Available from: 2005-09-13 Created: 2005-09-13 Last updated: 2011-09-23Bibliographically 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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Aspeborg, Henrik

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