Peptide Signals In Plants Research Articles

はじめに : 植物におけるペプチドシグナル伝達の最近の研究( 植物ペプチドシグナル)

はじめに : 植物におけるペプチドシグナル伝達の最近の研究( 植物ペプチドシグナル)

Posttranslationally modified small-peptide signals in plants.

Cell-to-cell signaling is essential for many processes in plant growth and development, including coordination of cellular responses to developmental and environmental cues. Cumulative studies have demonstrated that peptide signaling plays a greater-than-anticipated role in such intercellular communication. Some peptides act as signals during plant growth and development, whereas others are involved in defense responses or symbiosis. Peptides secreted as signals often undergo posttranslational modification and proteolytic processing to generate smaller peptides composed of approximately 10 amino acid residues. Such posttranslationally modified small-peptide signals constitute one of the largest groups of secreted peptide signals in plants. The location of the modification group incorporated into the peptides by specific modification enzymes and the peptide chain length defined by the processing enzymes are critical for biological function and receptor interaction. This review covers 20 years of research into posttranslationally modified small-peptide signals in plants.

Biological activity of nine recombinant AtRALF peptides: Implications for their perception and function in Arabidopsis

RALF is a small (5 kDa) and ubiquitous plant peptide signal. It was first isolated from tobacco leaf protein extracts owing to its capacity to alkalinize the extracellular media of cell suspensions. RALFs inhibit root growth and hypocotyl elongation, and a role for RALFs in cell expansion has also been proposed. Arabidopsis has 37 RALF isoforms (AtRALF), but only a small group of nine has high primary structure identity to the original RALF peptide isolated from tobacco. Herein, we report the heterologous production of these nine peptides in Escherichia coli and the evaluation of their activity in five biological assays. All AtRALF peptides produced showed strong alkalinizing activities, with the exception of the pollen-specific isoform AtRALF4. Although it exhibited no inhibitory activity in the root growth and hypocotyl elongation assays, AtRALF4 is a strong inhibitor of pollen germination. Our data demonstrate that the divergence in the tissue specificity and gene expression patterns of the different AtRALFs does not change the fact that their main role seems to be the regulation of cell expansion. Furthermore, different activities in the alkalinization assays upon the addition of two consecutive and saturating doses of the peptides suggest that the peptides are likely being sensed by specific receptors.

Plant elicitor peptides are conserved signals regulating direct and indirect antiherbivore defense

Insect-induced defenses occur in nearly all plants and are regulated by conserved signaling pathways. As the first described plant peptide signal, systemin regulates antiherbivore defenses in the Solanaceae, but in other plant families, peptides with analogous activity have remained elusive. In the current study, we demonstrate that a member of the maize (Zea mays) plant elicitor peptide (Pep) family, ZmPep3, regulates responses against herbivores. Consistent with being a signal, expression of the ZmPROPEP3 precursor gene is rapidly induced by Spodoptera exigua oral secretions. At concentrations starting at 5 pmol per leaf, ZmPep3 stimulates production of jasmonic acid, ethylene, and increased expression of genes encoding proteins associated with herbivory defense. These include proteinase inhibitors and biosynthetic enzymes for production of volatile terpenes and benzoxazinoids. In accordance with gene expression data, plants treated with ZmPep3 emit volatiles similar to those from plants subjected to herbivory. ZmPep3-treated plants also exhibit induced accumulation of the benzoxazinoid phytoalexin 2-hydroxy-4,7-dimethoxy-1,4-benzoxazin-3-one glucoside. Direct and indirect defenses induced by ZmPep3 contribute to resistance against S. exigua through significant reduction of larval growth and attraction of Cotesia marginiventris parasitoids. ZmPep3 activity is specific to Poaceous species; however, peptides derived from PROPEP orthologs identified in Solanaceous and Fabaceous plants also induce herbivory-associated volatiles in their respective species. These studies demonstrate that Peps are conserved signals across diverse plant families regulating antiherbivore defenses and are likely to be the missing functional homologs of systemin outside of the Solanaceae.

Identification of attractant LURE peptides for pollen tubes in Arabidopsis thaliana(<Feature Article>Plant Peptide Signals)

Identification of attractant LURE peptides for pollen tubes in Arabidopsis thaliana(<Feature Article>Plant Peptide Signals)

Regulation of inflorescence architecture by EPFL-type peptide hormones and their receptor(<Feature Article>Plant Peptide Signals)

Regulation of inflorescence architecture by EPFL-type peptide hormones and their receptor(<Feature Article>Plant Peptide Signals)

Regulation of plant vascular stem cell fate by TDIF peptide and TDR receptor(<Feature Article>Plant Peptide Signals)

Regulation of plant vascular stem cell fate by TDIF peptide and TDR receptor(<Feature Article>Plant Peptide Signals)

Root meristem growth factor, an secreted peptide signal involved in root meristem development(<Feature Article>Plant Peptide Signals)

Root meristem growth factor, an secreted peptide signal involved in root meristem development(<Feature Article>Plant Peptide Signals)

Chemical Synthesis of Arabidopsis CLV3 Glycopeptide Reveals the Impact of Hydroxyproline Arabinosylation on Peptide Conformation and Activity

Arabinosylation of hydroxyproline (Hyp) is a post-translational modification often found in secreted peptide signals in plants. The physiological importance of this modification was highlighted by the finding that CLAVATA3 (CLV3), a key peptide signal for regulating the fate of stem cells in the shoot apical meristem in Arabidopsis, contains three l-arabinose residues linked via linear β-1,2-linkages. However, understanding the functions and properties of arabinosylated peptides has been hindered by difficulties in synthesizing the complex arabinose chain. Here we report the stereoselective total synthesis of β-1,2-linked triarabinosylated CLV3 peptide ([Ara3]CLV3). Chemically synthesized [Ara3]CLV3 restricted stem cell activity more effectively than did unmodified CLV3 peptide. Comparison of mono-, di- and triarabinosylated CLV3 glycopeptides revealed that the biological activity increased progressively as the arabinose chain length increased. Thus, the arabinose chain length of CLV3 is important for its biological activity. Nuclear magnetic resonance spectroscopy and nuclear Overhauser effect-based structure calculations further revealed the structural impact of the arabinose chain on peptide conformation. The arabinose chain of [Ara3]CLV3 extends toward the C-terminal end of the peptide, and its non-reducing end is positioned proximal to the peptide backbone. Consequently, the arabinose chain causes distinct distortion in the C-terminal half of the peptide in a highly directional manner. The established synthetic route of [Ara3]CLV3 will greatly contribute to our understanding of the biology and biochemistry of arabinosylated peptide signals in plants.

Recent progress in research on small post‐translationally modified peptide signals in plants

Peptide signaling plays a major role in various aspects of plant growth and development, as has been shown in recent biochemical, genetic and bioinformatic studies. There are over a dozen secreted peptides recognized in plants known to regulate cellular functions. To become functional, these secreted peptide signals often undergo post‐translational modifications, such as tyrosine sulfation, proline hydroxylation, and hydroxyproline arabinosylation, and successive proteolytic processing. These types of ‘small post‐translationally modified peptide signals’ are one of the major groups of peptide signals found in plants. In parallel with the discovery of peptide signals, specific receptors for such peptide signals were identified as being membrane‐localized leucine‐rich repeat receptor kinases. This short review highlights the recent progress in research on small post‐translationally modified peptide signals, including our own research.

Small Post-Translationally Modified Peptide Signals in Arabidopsis

Recent biochemical, genetic and bioinformatic studies have demonstrated that peptide signaling plays a greater than anticipated role in various aspects of plant growth and development. More than a dozen secreted peptides are now recognized as important signals that mediate cell-to-cell communication. Secreted peptide signals often undergo post-translational modification and proteolytic processing, which are important for their function. Such "small post-translationally modified peptide signals" constitute one of the largest groups of peptide signals in plants. In parallel with the discovery of peptide signals, specific receptors for such peptides were identified as being membrane-localized receptor kinases, the largest family of receptor-like molecules in plants. These findings illustrate the critical roles of small peptide ligand-receptor pairs in plant growth and development. This review outlines recent research into secreted peptide signals in plants by focusing on small post-translationally modified peptides.

Evolutionary advantages of secreted peptide signalling molecules in plants

Peptide signalling molecules create diverse modular signals in animal systems, but it is only relatively recently that an expanding array of peptide signalling groups has been identified in plants. Representatives occur in moss although most are in angiosperms (both monocot and dicot) including many agronomically important crops. Some groups show high diversity within a species, whereas other peptide signalling groups are small or represented by a single peptide or only found in a single family of plants. Plant peptide signals regulate meristem organogenesis and growth, modulate plant homeostasis and growth, and recognise damage or imminent danger from pathogen attack. The peptide signalling molecules are secreted into the apoplast where they are often further proteolytically processed before acting on receptors in nearby or adjacent cells with all the hallmarks of paracrine molecules. Where the receptors have been identified, they are receptor-like kinases that form oligomers upon peptide binding and relay messages via phosphorylation cascades. The use of nitrogen rich amino acids in the signalling peptides was analysed and nitrogen scores were obtained that are higher than the mean nitrogen score for the overall average of the Arabidopsis proteome. These findings are discussed in terms of nutritional availability and energy use.

Structure–activity studies of AtPep1, a plant peptide signal involved in the innate immune response

AtPep1, a 23-amino acid peptide recently isolated from Arabidopsis leaves, induces the expression of the genes encoding defense proteins against pathogens. We investigated the structure–activity relationship of AtPep1 with its receptor, a 170 kDa leucine-rich repeat receptor kinase ( AtPEPR1) by utilizing a suspension cell assay (the alkalinization assay). Binding of AtPep1 to AtPEPR1 on the cell surface is accompanied by an increase in the pH of Arabidopsis suspension cell media by 1 pH unit in 15 min with a half-maximal response of 0.25 nM. Sequential removal of N-terminal amino acids had little effect on activity until the peptide was reduced to 15 amino acids [ AtPep1(9–23)], which decreased the activity by less than one order of magnitude. Activity was completely abolished when nine C-terminal amino acids remained. Removal of the C-terminal asparagine from AtPep1(9–23), resulted in a decrease in activity ( 1 2 max ∼ 100 nM). AtPep1(9–23) was used for alanine-substitution analysis and revealed two important residues for activity, a serine, [A 15] AtPep1(9–23) ( 1 2 max ∼ 10 nM), and a glycine, [A 17] AtPep1(9–23) ( 1 2 max ∼ 1000 nM). Neither [A 17] AtPep1(9–23) nor the C-terminal truncated AtPep1, AtPep1(9–22), were able to compete with AtPep1(9–23) in the alkalinization assay. The importance of the glycine residue for binding to the AtPep receptor was also confirmed by competition assays using radiolabeled AtPep1. d-Alanine or 2-methylalanine substituted at the glycine position displayed only a slight decrease in activity whereas l- and d-proline substitution caused a loss of activity. Homologs of AtPep1 identified in Arabidopsis and other species revealed a strict conservation of the glycine residue.