Specific pools of endogenous peptides are present in gametophore, protonema, and protoplast cells of the moss Physcomitrella patens

Abstract

BackgroundProtein degradation is a basic cell process that operates in general protein turnover or to produce bioactive peptides. However, very little is known about the qualitative and quantitative composition of a plant cell peptidome, the actual result of this degradation. In this study we comprehensively analyzed a plant cell peptidome and systematically analyzed the peptide generation process.ResultsWe thoroughly analyzed native peptide pools of Physcomitrella patens moss in two developmental stages as well as in protoplasts. Peptidomic analysis was supplemented by transcriptional profiling and quantitative analysis of precursor proteins. In total, over 20,000 unique endogenous peptides, ranging in size from 5 to 78 amino acid residues, were identified. We showed that in both the protonema and protoplast states, plastid proteins served as the main source of peptides and that their major fraction formed outside of chloroplasts. However, in general, the composition of peptide pools was very different between these cell types. In gametophores, stress-related proteins, e.g., late embryogenesis abundant proteins, were among the most productive precursors. The Driselase-mediated protonema conversion to protoplasts led to a peptide generation “burst”, with a several-fold increase in the number of components in the latter. Degradation of plastid proteins in protoplasts was accompanied by suppression of photosynthetic activity.ConclusionWe suggest that peptide pools in plant cells are not merely a product of waste protein degradation, but may serve as important functional components for plant metabolism. We assume that the peptide “burst” is a form of biotic stress response that might produce peptides with antimicrobial activity from originally functional proteins. Potential functions of peptides in different developmental stages are discussed.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-015-0468-7) contains supplementary material, which is available to authorized users.

The Plant Peptidome: An Expanding Repertoire of Structural Features and Biological Functions

“…For example, in gametophore, protonema, and protoplast cells of the moss Physcomitrella patens, more than 20,000 unique endogenous peptides ranging from 5 to 78 amino acids were detected with mass spectrometry analysis (Fesenko et al, 2015). These specific peptide pools are hydrolysis products of functional proteins, although the exact mechanisms of endogenous peptide formation have not been elucidated yet.…”

“…In both the protonema and protoplast states of the moss, plastid proteins served as the main source of peptides. In gametophores, stress-related proteins were among the most productive precursors (Fesenko et al, 2015). The functional characterization of endogenous peptide pools is ongoing, though 117 peptides already were predicted to have antimicrobial potential (Torrent et al, 2012;Fesenko et al, 2015).…”

“…The functional characterization of endogenous peptide pools is ongoing, though 117 peptides already were predicted to have antimicrobial potential (Torrent et al, 2012;Fesenko et al, 2015). It is hypothesized that the formation of these specific endogenous peptide pools or "peptide burst" is a form of biotic stress response based on the production of AMPs from existing functional proteins (Fesenko et al, 2015). Nevertheless, experimental evidence on the bioactivity of these endogenous peptides is essential to consider them as functional components of plant metabolism and not as degradation products of the proteome.…”

“…In gametophores, stress-related proteins were among the most productive precursors (Fesenko et al, 2015). The functional characterization of endogenous peptide pools is ongoing, though 117 peptides already were predicted to have antimicrobial potential (Torrent et al, 2012;Fesenko et al, 2015). It is hypothesized that the formation of these specific endogenous peptide pools or "peptide burst" is a form of biotic stress response based on the production of AMPs from existing functional proteins (Fesenko et al, 2015).…”

“…Evidence is emerging on bioactive peptides formed from functional protein precursors that are suggested to serve (themselves) as important functional components of plant metabolism (Fesenko et al, 2015). For example, in gametophore, protonema, and protoplast cells of the moss Physcomitrella patens, more than 20,000 unique endogenous peptides ranging from 5 to 78 amino acids were detected with mass spectrometry analysis (Fesenko et al, 2015).…”