First published online March 18, 2008; 10.1105/tpc.108.200312
The Plant Cell 20:500
Cellulose Synthesis in Phytophthora infestans Pathogenesis
Jennifer Mach
Science Editor
jmach{at}aspb.org
Plant pathogens breach the plant cell to reach the nutrients within and yet must also avoid detection by the plant defenses (reviewed in Huckelhoven, 2007 ). During infection, fungal and oomycete pathogens make new cell wall and at the same time break down the host cell wall. First, the pathogen synthesizes the new cell wall to make infection-associated structures. Second, the pathogen breaks down the physical barrier of the plant cell wall by both enzymatic action and/or mechanical pressure, depending on the infection strategy of the pathogen. Unlike most fungal pathogens, which have chitin-based cell walls, the oomycete pathogen Phytophthora infestans has a cell wall composed mainly of cellulose. Cellulose synthesis in plants involves regulation of two groups of cellulose synthases (CesA), specific for primary and secondary cell wall formation (reviewed in Joshi and Mansfield, 2007), but the role of cellulose synthesis in P. infestans has not been comprehensively examined.
In this issue of The Plant Cell, Grenville-Briggs et al. (pages 720–738) investigate cellulose synthesis in P. infestans pathogenesis. They isolate a novel family of four P. infestans cellulose synthases (CesA1 through 4), which are similar to plant CesA proteins but most closely related to cellulose synthases from cyanobacteria. The P. infestans CesA proteins have the transmembrane domain structure and signature motifs of processive glycosyltransferases but also have a pleckstrin homology domain of unclear function. These proteins are upregulated during early infection stages and localize to the growing tip of the infection structures. The authors examine the role of the CesA proteins and cellulose synthesis in infection using RNA interference to reduce expression of all four CesA proteins simultaneously and by examining pathogen function in the presence of the cellulose synthesis inhibitor 2,6-dichlorobenzonitrile (DCB). P. infestans lines expressing reduced amounts of the CesA family show perturbed cell wall structure, reduced cellulose content, and aberrant morphology of infection-associated structures. Similarly, wild-type P. infestans treated with DCB show similar phenotypes and a complete inability to infect potato cells (see figure)
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Synthesis of cellulose is essential for proper infection of potato epidermal cells. Wild-type P. infestans produces a short germ tube and makes an appressorium that penetrates the epidermal cell (A). In the presence of the cellulose synthesis inhibitor DCB, the germ tube produces multiple appressorium-like structures but fails to penetrate the epidermal cell (B).
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This work shows that P. infestans requires cellulose synthesis to penetrate potato cells and establish successful infection. The new cell wall formed is likely required to produce infection structures to achieve the proximity and generate the force required to break through the plant cell wall. Further work in this field will better elucidate this mechanism and address the intriguing question of how P. infestans breaks down plant cellulose without breaking down its own cell wall.
Footnotes
www.plantcell.org/cgi/doi/10.1105/tpc.108.200312
REFERENCES
Grenville-Briggs, L.J., Anderson, V.L., Fugelstad, J., Avrova, A.O., Bouzenzana, J., Williams, A., Wawra, S., Whisson, S.C., Birch, P.R.J., Bulone, V., and van West, P. (2008). Cellulose synthesis in Phytophthora infestans is required for normal appressorium formation and successful infection of potato. Plant Cell 20: 720–738.[Abstract/Free Full Text] Huckelhoven, R. (2007). Cell wall-associated mechanisms of disease resistance and susceptibility. Annu. Rev. Phytopathol. 45: 101–127.[CrossRef][ISI][Medline] Joshi, C.P., and Mansfield, S.D. (2007). The cellulose paradox – Simple molecule, complex biosynthesis. Curr. Opin. Plant Biol. 10: 220–226.[CrossRef][Medline]
Related articles in Plant Cell:
- Cellulose Synthesis in Phytophthora infestans Is Required for Normal Appressorium Formation and Successful Infection of Potato
- Laura J. Grenville-Briggs, Victoria L. Anderson, Johanna Fugelstad, Anna O. Avrova, Jamel Bouzenzana, Alison Williams, Stephan Wawra, Stephen C. Whisson, Paul R.J. Birch, Vincent Bulone, and Pieter van West
Plant Cell 2008 20: 720-738.
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