In multicellular organisms, cell to cell communication is essential for co-ordinating the growth and differentiation. In animals, signalling peptides are known to be the major players in neural communication (for review, see Alberts et al., 1994,Molecular Biology of the Cell). This is in contrast to plants in which most intercellular communication is mediated by phytohormones such as auxin, cytokinin, GA, ABA, ethylene and brassinosteroids (Kende et al., 1997, Plant Cell 9:1197-1210; Mandave et al., 1988, Annu. Rev. Plant Phys. Plant Mol. Biol. 39:23-52). In recent years, several putative peptide ligands have been identified in plants (Ryan et al., 2002; Lindsey et al., 2002) and have been shown to mediate signalling events during plant-pathogen interactions (Pearce et al., 1992), cell division (Matsubayashi et al., 1996) and anther-stigma interactions (Schopfer et al., 1999; Kim et al., 2003).
In our lab, we intend to understand how CLV3 and other genes in the same family, such as CLE19, function in plants. We have showed that CLE 19 is expressed in the differentiating cells, such as the periphery of shoot apical meristem. Over-expression of CLE19 leads to the consumption of the root meristems (Fiers et al., 2004). In collaboration with the Scheres lab in Utrecht, we have discovered two genetic loci, SOL1 and SOL2, that could lead to the suppression of the over-expression phenotype after mutation (Casamitjana-Martinez et al., 2003). SOL1 was been identified through position cloning, which encodes a carboxylpeptidase, suggesting that CLE19 functions through processed peptides.
CLAVATA3 (CLV3) functions as a putative peptide ligand that acts through the CLV1/CLV2 receptor complex to restrict the number of stem cells in the shoot apical meristem, but the biochemical nature of the ligand remains unknown. Overexpression of CLV3, or of related genes CLE19 or CLE40, leads to termination of meristem development. We (see Fiers et al., 2005) hypothesize that the active part of the encoded proteins lies within a conserved 14-amino acid CLE motif. We demonstrated that synthetic peptides corresponding to this motif trigger consumption of the root meristem in vitro and that these peptides act through a CLV2-containing receptor complex to interfere with the specification of cell identities. The cover image shows abnormal expression of a cortex-specific yellow fluorescent protein marker in an increased number of ground tissue daughter cells (outlined in green) and in endodermis cells (outlined in white) of roots treated with CLE19 peptide.
References:
- E. Casamitjana-Martínez, H. F. Hofhuis, J. Xu, C.M. Liu, R. Heidstra and B. Scheres (2003) Root-Specific CLE19 Overexpression and the sol1/2: Suppressors Implicate a CLV-like Pathway in the Control of Arabidopsis Root Meristem. Current Biology, 13: 1435-1441
- M. Fiers, G. Hause, K. Boutilier, E. Casamitjana-Marinez, D. Weijers, R. Offringa, L. van der Geest, M. van Lookeren Campagne, CM. Liu (2004) Mis-expression of the CLV3/ESR-like gene CLE19 in Arabidopsis leads to a consumption of root meristem. Gene, 327:37-49.
- Martijn Fiers, Elzbieta Golemiec, Jian Xu, Lonneke van der Geest, Renze Heidstra, Willem Stiekema, and Chun-Ming Liu (2005). The 14–Amino Acid CLV3, CLE19, and CLE40 Peptides Trigger Consumption of the Root Meristem in Arabidopsis through a CLAVATA2-Dependent Pathway. Plant Cell 2005 17: 2542-2553
Recent posters: