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Cellulose Biosynthesis in Oomycetes
KTH, School of Biotechnology (BIO), Glycoscience.
2008 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

Oomycetes have long been considered as a separate class within the kingdom Fungi, but they are in fact closer to brown algae. They are currently classified in the Stramenopile eukaryotic kingdom, which includes heterokont algae and water molds. The major cell wall polysaccharides in Oomycetes are b-(1à3) and b-(1à6)-glucans, as well as cellulose, which has never been reported in any fungal species. Chitin - the major cell wall polysaccharide in fungi - occurs in minor amounts in the walls of some Oomycetes. Some Oomycete species are pathogens of great economical importance. For example, species of the genus Phytophthora are well studied plant pathogens that cause considerable economical losses in agriculture. Saprolegniosis, a fish disease caused by species from the genus Saprolegnia, is a major problem in the aquaculture industry and represents a threat to populations of salmonids in natural habitats. Currently, there are no chemicals available that are at the same time efficient Oomycete inhibitors, environmentally friendly and safe for human consumption of treated fishes. The biosynthesis of cellulose in Oomycetes is poorly understood, even though this biochemical pathway represents a potential target for new Oomycete inhibitors. In this work, cellulose biosynthesis was investigated in two selected Oomycetes, the plant pathogen Phytophthora infestans and the fish pathogen Saprolegnia monoica.

A new Oomycete CesA gene family was identified. It contains four homologues designated as CesA1, CesA2, CesA3 and CesA4. The gene products of CesA1, 2 and 4 contain Pleckstrin Homology domains located at the N-terminus. This represents a novel feature, unique to the Oomycete CesA genes. CesA3 is the dominantly expressed CesA homologue in the mycelium of both S. monoica and P. infestans, while CesA1 and CesA2 are up-regulated in virulent life stages of P. infestans. CesA4 was expressed only in minute amounts in all investigated types of cells. Gene silencing by RNA interference of the whole CesA gene family in P. infestans lead to decreased amounts of cellulose in the cell wall. The inhibitors of cellulose synthesis DCB and Congo Red had an up-regulating effect on SmCesA gene expression, which was accompanied by an increased b-glucan synthase activity in vitro. In addition, these inhibitors slowed down the growth of the mycelium from S. monoica. Zoospores from P. infestans treated with DCB were unable to infect potato leaves and showed aberrant cell wall morphologies similar to those obtained by silencing the CesA gene family.

Altogether these results show that at least some of the CesA1-4 genes are involved in cellulose biosynthesis and that the synthesis of cellulose is crucial for infection of potato by P. infestans

Place, publisher, year, edition, pages
Stockholm: KTH , 2008. , 40 p.
Series
Trita-BIO-Report, ISSN 1654-2312 ; 2008:13
Keyword [en]
cellulose biosynthesis, cellulose synthase genes, Oomycetes, Phytophthora infestans, Saprolegnia monoica.
National Category
Other Industrial Biotechnology
Identifiers
URN: urn:nbn:se:kth:diva-9282ISBN: 978-91-7415-034-6 (print)OAI: oai:DiVA.org:kth-9282DiVA: diva2:54419
Presentation
2008-08-22, FA32 AlbaNova, Stockholm, 10:00 (English)
Supervisors
Note
QC 20101110Available from: 2008-10-16 Created: 2008-10-16 Last updated: 2010-11-10Bibliographically approved
List of papers
1. Cellulose synthesis in Phytophthora infestans is required for normal appressorium formation and successful infection of potato
Open this publication in new window or tab >>Cellulose synthesis in Phytophthora infestans is required for normal appressorium formation and successful infection of potato
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2008 (English)In: The Plant Cell, ISSN 1040-4651, E-ISSN 1532-298X, Vol. 20, no 3, 720-738 p.Article in journal (Refereed) Published
Abstract [en]

Cellulose, the important structural compound of cell walls, provides strength and rigidity to cells of numerous organisms. Here, we functionally characterize four cellulose synthase genes (CesA) in the oomycete plant pathogen Phytophthora infestans, the causal agent of potato (Solanum tuberosum) late blight. Three members of this new protein family contain Pleckstrin homology domains and form a distinct phylogenetic group most closely related to the cellulose synthases of cyanobacteria. Expression of all four genes is coordinately upregulated during pre- and early infection stages of potato. Inhibition of cellulose synthesis by 2,6-dichlorobenzonitrile leads to a dramatic reduction in the number of normal germ tubes with appressoria, severe disruption of the cell wall in the preinfection structures, and a complete loss of pathogenicity. Silencing of the entire gene family in P. infestans with RNA interference leads to a similar disruption of the cell wall surrounding appressoria and an inability to form typical functional appressoria. In addition, the cellulose content of the cell walls of the silenced lines is >50% lower than in the walls of the nonsilenced lines. Our data demonstrate that the isolated genes are involved in cellulose biosynthesis and that cellulose synthesis is essential for infection by P. infestans.

Keyword
fungus saprolegnia-monoica, v chitin synthase, cell-walls, sequence, alignment, plant interactions, in-vitro, biosynthesis, oomycete, gene, enzymes
National Category
Industrial Biotechnology
Identifiers
urn:nbn:se:kth:diva-17577 (URN)10.1105/tpc.107.052043 (DOI)000256415500020 ()2-s2.0-48249119647 (Scopus ID)
Note
QC 20100525 Rättelse publicerad i Plant cell, vol. 20, nr 6, 2008.Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
2. A novel family of cellulose synthase genes from the Oomycete Saprolegnia monoica: functional characterization using cellulose synthesis inhibitors
Open this publication in new window or tab >>A novel family of cellulose synthase genes from the Oomycete Saprolegnia monoica: functional characterization using cellulose synthesis inhibitors
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(English)Manuscript (Other academic)
National Category
Industrial Biotechnology
Identifiers
urn:nbn:se:kth:diva-9281 (URN)
Note
QC 20101110Available from: 2008-10-16 Created: 2008-10-16 Last updated: 2010-11-10Bibliographically approved

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