ROTUNDIFOLIA4 Regulates Cell Proliferation Along the Body Axis in Arabidopsis Shoot

Abstract

Molecular genetics has been successful in identifying leaf- size regulators such as transcription factors, phytohormones, and signal molecules. Among them, a ROTUNDIFOLIA4-LIKE/DEVIL (RTFL/DVL) family of Arabidopsis, genes encoding peptides with no secretion-signal sequence, is unique in that their overexpressors have a reduced number of leaf cells specifically along the proximodistal axis. However, because the RTFL/DVL lack any obvious homology with functionally identified domains, and because of genetic redundancy among RTFL/DVL, their molecular and developmental roles are unclear. In this study we focused on one member in the family, ROTUNDIFOLIA4 (ROT4), and identified the core functional region within it and we found no proteolytic processing in planta. Developmental analysis of leaf primordia revealed that ROT4 overexpression reduces the meristematic zone size within the leaf blade. Moreover, induced local overexpression demonstrated that ROT4 acts as a regulator of the leaf shape via a change in positional cue along the longitudinal axis. Similarly, ROT4 overexpression results in a protrusion of the main inflorescence stem, again indicating a change in positional cue along the longitudinal axis. These results suggest that ROT4 affects the positional cue and cell proliferation along the body axis.

Size Control in Plants—Lessons from Leaves and Flowers

“…Not indicated are the factors PEAPOD1/PEAPOD2, which inhibit the proliferation of dispersed meristematic cells, and thus support the progression of a secondary arrest front. The following factors have not been discussed in detail in the main text: Rotundifolia4 (ROT4) (Ikeuchi et al 2011), Ngatha (NGA) (Alvarez et al 2009), Spatula (SPT) , Struwwelpeter (SWP) (Autran et al 2002), ARGOS-LIKE (ARL) (Hu et al 2006), and CYP78A7 (a homolog of KLUH/ CYP78A5) (Wang et al 2008). TOR, Target of rapamycin; RAPTOR, regulatory-associated protein of TOR; GRF, growth-regulating factor; GIF, GRF interacting factor.…”

“…Under this scenario, changes in the rate of cell production should modify organ size. Indeed, when the rate of cell production is altered because of either a change in the pace of cell cycling or of the size of the proliferative area at the base of the leaf, corresponding changes in organ size are seen (Ferjani et al 2007;Lee et al 2009;Rojas et al 2009;Ichihashi et al 2010;Ikeuchi et al 2011). A number of mutants are known that prolong or reduce the duration of the proliferation phase (see below).…”

The Alteration of Plant Morphology by Small Peptides Released from the Proteolytic Processing of the Bacterial Peptide TENGU

“…Similar to TENGU, which is released inside plant phloem cells and affects host development, some bioactive peptides, including ROTUNDIFOLIA4 (ROT4), are thought to act inside cells to regulate plant morphology. The peptide ROT4, of which the core functional region is the 30-to 34-amino acid central region, is involved in leaf development and is not thought to be processed (Narita et al, 2004;Ikeuchi et al, 2011). Although there is no known homology in the amino acid sequence, there might be a functional similarity between TENGU and these intracellular bioactive peptides.…”

A Plant Small Polypeptide Is a Novel Component of DNA-Binding Protein Phosphatase 1-Mediated Resistance to Plum pox virus in Arabidopsis

“…Peptides have been shown to play important roles in cell-cell communication and signaling processes (Farrokhi et al, 2008). Although many of these peptides undergo proteolytic processing and are secreted to the extracellular space, there also exist intracellular peptides that do not show apparent secretion or processing, like peptides of the ROT4 family (Ikeuchi et al, 2011). NtDIP2 represents a novel class of intracellular peptides, since, according to the SignalP program (Bendtsen et al, 2004), it lacks any signal sequence.…”