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Arabidopsis 2010 Project:

The CLE Family of CLV3-Like Proteins

Plant growth and survival is critically dependent on the communication of information between cells. Cell to cell signaling is essential for many processes, including coordination of cellular responses to environmental and developmental stimuli. A large proportion of the Arabidopsis thaliana genome appears to be dedicated to intercellular communication, as 10% of the 25,498 predicted proteins are classified as playing potental roles in signal transduction.

One of the few known Arabidopsis polypeptide signaling molecules is the CLAVATA3 (CLV3) protein(1). CLV3 is a small secreted(2) factor that communicates stem cell fate information in shoot and floral meristems(3), via a negative regulatory feedback loop that involves a receptor-like kinase and a downstream signaling cascade(4). CLV3 is a founding member of the plant-specific CLE family of putative polypeptide signaling molecules(5), which share a short 14 amino acid carboxyl terminal region of sequence similarity with CLV3 and three maize ESR proteins. Our results have shown that 24 out of the 25 Arabidopsis CLE genes encode transcripts that can be detected in one or more tissues under normal developmental conditions(6). Each Arabidopsis CLE protein is predicted to encode small polypeptides of 80-120 amino acids that contain an amino terminal signal peptide or signal anchor, targeting the protein to the secretory pathway. Thus these proteins may mediate signaling between cells by acting as extracellular ligands for some of the 216 receptor-like kinases in the Arabidopsis genome.

References

1. Fletcher, J.C., Brand, U., Running, M.P., Simon, R. and Meyerowitz, E.M. (1999). Communication of cell fate decisions by CLAVATA3 in Arabidopsis shoot meristems. Science 283: 1911-1914.

2. Rojo, E., Sharma, V.K., Kovaleva, V., Raikhel, N.V. and Fletcher, J.C. (2002). CLV3 is localized to the extracellular space where it activates the Arabidopsis CLAVATA stem cell signaling pathway. Plant Cell 14: 1-10.

3. Brand, U., Fletcher, J.C., Hobe, M., Meyerowitz, E.M. and Simon, R. (2000). Stem cell fate in Arabidopsis depends on a feedback loop regulated by CLV3 activity. Science 289: 617-619.

4. Fletcher, J.C. (2002). Shoot and floral meristem maintenance in Arabidopsis. Annual Review of Plant Biology 53: 45-66.

5. Cock, J. M. and McCormick, S. (2001). A large family of genes that share homology with CLAVATA3. Plant Physiology 126: 939-942.

6. Sharma, V.K., Ramirez, J. and Fletcher, J.C. (2003). The Arabidopsis CLV3-like (CLE) genes are expressed in diverse tissues and encode secreted proteins. Plant Molecular Biology 51:415-425.


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