Small (~5-50 amino acid), secreted, peptide signals encoded by over 10 plant multigene families mediate cell-to-cell communication and play important roles in controlling diverse developmental processes. Amongst these, CEP (C-TERMINALLY ENCODED PEPTIDE) genes are found in more recently emerged plant lineages and, surprisingly, in root knot nematodes but not ancient plant lineages 1-3. CEPs are 15 amino acid post-translationally modified peptides that affect root and shoot development. Abiotic factors, such as low nitrogen (N) and high salt, induce CEP gene expression in Arabidopsis and Medicago 1,4. The Arabidopsis AtCEP3 gene negatively regulates root development. Primary root growth is slowed by AtCEP3 over-expression or by the exogenous application of the AtCEP3 peptide which decreases meristem size. Consistently, cep3 knock-out mutants show enhanced root growth under abiotic stress conditions and have a larger meristematic zone. AtCEP3 mis-regulation perturbs cell cycle progression but not stem cell maintenance or patterning. In contrast, the N-limitation induced Medicago MtCEP1 gene encodes for two CEP peptide domains which suppress lateral root emergence but enhances root nodule formation without unaffecting primary root growth. The two MtCEP1 peptides affect different stages of lateral root development. We propose that CEPs provide a link between environmental stimuli and the control of root development.
Biography: Associate Professor Michael Djordjevic is a Laboratory Leader in the Plant Science Division in the Research School of Biology at the Australian National University. His undergraduate studies were at the University of Queensland where he completed a B.Sc with first class honours. He completed his PhD as the Australian National University in 1984. His career has spanned several research areas: the identification of new biologically active signalling molecules in plants (focussing on flavonoids), identifying bioactive molecules that bridge between plant and animal systems and he has been a pioneer in proteomic technologies and applying them to unravel important biological questions. His major research interests lie in understanding the legume-Rhizobium symbiosis and how small, endogenous, secreted, regulatory peptides modulate the interactions between the environmental and the control of plant root development. Most recently he has focused on the CEP peptide family in the Arabidopsis and Medicago model systems.