[Plant signaling peptides. Small post-translationally modified peptides]

Recent genetic, bioinformatic and biochemical analyses have revealed that many secretory peptides are important components in intercellular signaling that coordinate and specify cellular functions in plants. The signaling peptides discovered in plants thus far can be considered to fall into two broad groups. Peptides from the first group are undergo post-translational modification, such as proline hydroxylation, hydroxyproline arabinosylation or tyrosine sulfation. Peptides from the second group are defined as cysteine-rich peptides (CRPs). The Cys-rich peptides are larger and they contain 4 to 16 cysteine residues. In parallel with the discovery of plant signal peptides, specific receptors for such peptide signals are identified. So far, the receptors for plant peptides that have been identified are members of the receptor-like kinases (RLKs) and the receptor-like proteins (RLPs) families, and most of them contain leucine-rich repeat (LRR) extracellular domain. The present review presents the recent progress in research on small post-translationally modified signal peptides. Recent findings indicate that these peptides are involved in various aspects of plant growth regulation including meristem organization, primary root development, lateral root initiation, vasculature development, organ abscission, and root nodulation.