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Eukaryotic Cell, April 2002, p. 281-292, Vol. 1, No. 2
1535-9778/02/$04.00+0     DOI: 10.1128/EC.1.2.281-292.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

Outside-In Signaling of Cellulose Synthesis by a Spore Coat Protein in Dictyostelium

Christopher M. West,* Ping Zhang, Aiko C. McGlynn, and Lee Kaplan

Department of Anatomy and Cell Biology, College of Medicine, University of Florida, Gainesville, Florida 32610-0235

Received 10 October 2001/ Accepted 24 January 2002

The spore coat of Dictyostelium is formed de novo from proteins secreted from vesicles and cellulose synthesized across the plasma membrane as differentiating spores rise up the stalk. The mechanism by which these events are coordinated is not understood. In the course of experiments designed to test the function of the inner layer coat protein SP85 (PsB), expression of a specific partial length fragment was found to interrupt coat assembly after protein secretion and prior to cellulose synthesis in 85% of the cells. This fragment consisted of SP85's N-terminal domain, containing prespore vesicle targeting information, and its Cys-rich C1 domain. The effect of the NC1 fusion was not cell autonomous in interstrain chimeras, suggesting that it acted at the cell surface. SP85-null spores presented an opposite phenotype in which spores differentiated prematurely before reaching the top of the stalk, and cellulose was slightly overproduced in a disorganized fashion. A similar though less severe phenotype occurred when a fusion of the N and C2 domains was expressed. In a double mutant, absence of SP85 was epistatic to NC1 expression, suggesting that NC1 inhibited SP85 function. Together, these results suggest the existence of an outside-in signaling pathway that constitutes a checkpoint to ensure that cellulose synthesis does not occur until coat proteins are properly organized at the cell surface and stalk formation is complete. Checkpoint execution is proposed to be regulated by SP85, which is in turn under the influence of other coat proteins that interact with SP85 via its C1 and C2 domains.

* Corresponding author. Mailing address: P.O. Box 100235, 1600 SW Archer Rd., University of Florida College of Medicine, Gainesville, FL 32610-0235. Phone: (352) 392-3329. Fax: (352) 392-3305. E-mail: westcm{at}ufl.edu.

Eukaryotic Cell, April 2002, p. 281-292, Vol. 1, No. 2
1535-9778/02/$04.00+0     DOI: 10.1128/EC.1.2.281-292.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • West, C. M., Nguyen, P., van der Wel, H., Metcalf, T., Sweeney, K. R., Blader, I. J., Erdos, G. W. (2009). Dependence of Stress Resistance on a Spore Coat Heteropolysaccharide in Dictyostelium. Eukaryot Cell 8: 27-36 [Abstract] [Full Text]  
  • Metcalf, T., van der Wel, H., Escalante, R., Sastre, L., West, C. M. (2007). Role of SP65 in Assembly of the Dictyostelium discoideum Spore Coat. Eukaryot Cell 6: 1137-1149 [Abstract] [Full Text]  
  • Kwok, A. C.M., Wong, J. T.Y. (2003). Cellulose Synthesis Is Coupled to Cell Cycle Progression at G1 in the Dinoflagellate Crypthecodinium cohnii. Plant Physiol. 131: 1681-1691 [Abstract] [Full Text]  


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