Abstract
BackgroundSmall, secreted signaling peptides work in parallel with phytohormones to control important aspects of plant growth and development. Genes from the C-TERMINALLY ENCODED PEPTIDE (CEP) family produce such peptides which negatively regulate plant growth, especially under stress, and affect other important developmental processes. To illuminate how the CEP gene family has evolved within the plant kingdom, including its emergence, diversification and variation between lineages, a comprehensive survey was undertaken to identify and characterize CEP genes in 106 plant genomes.ResultsUsing a motif-based system developed for this study to identify canonical CEP peptide domains, a total of 916 CEP genes and 1,223 CEP domains were found in angiosperms and for the first time in gymnosperms. This defines a narrow band for the emergence of CEP genes in plants, from the divergence of lycophytes to the angiosperm/gymnosperm split. Both CEP genes and domains were found to have diversified in angiosperms, particularly in the Poaceae and Solanaceae plant families. Multispecies orthologous relationships were determined for 22% of identified CEP genes, and further analysis of those groups found selective constraints upon residues within the CEP peptide and within the previously little-characterized variable region. An examination of public Oryza sativa RNA-Seq datasets revealed an expression pattern that links OsCEP5 and OsCEP6 to panicle development and flowering, and CEP gene trees reveal these emerged from a duplication event associated with the Poaceae plant family.ConclusionsThe characterization of the plant-family specific CEP genes OsCEP5 and OsCEP6, the association of CEP genes with angiosperm-specific development processes like panicle development, and the diversification of CEP genes in angiosperms provides further support for the hypothesis that CEP genes have been integral to the evolution of novel traits within the angiosperm lineage. Beyond these findings, the comprehensive set of CEP genes and their properties reported here will be a resource for future research on CEP genes and peptides.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-870) contains supplementary material, which is available to authorized users.
Highlights
Small, secreted signaling peptides work in parallel with phytohormones to control important aspects of plant growth and development
Canonical C-TERMINALLY ENCODED PEPTIDE (CEP) genes identified in gymnosperms and angiosperms To identify canonical CEP genes, 106 plant genome assemblies (Additional file 1: Table S1) spanning 80 genera and 39 families across the plant kingdom were scanned for open reading frames (ORF) with an N-terminal secretion signal (NSS) and one or more canonical CEP domains
Using a positionspecific probability matrix (PSPM) iteratively generated from previously identified CEP domains (Additional file 2), 916 CEP genes and 1,223 CEP domains were identified across seed plants (Table 1)
Summary
Small, secreted signaling peptides work in parallel with phytohormones to control important aspects of plant growth and development. Genes from the C-TERMINALLY ENCODED PEPTIDE (CEP) family produce such peptides which negatively regulate plant growth, especially under stress, and affect other important developmental processes. It is recognized that these peptides work in parallel with One of these families is the C-TERMINALLY ENCODED PEPTIDE (CEP) gene family. The paucity of CEP mutants has hampered detailed analyses of function, but overexpression and reporter gene studies suggest CEP peptides play important roles in a wide variety of processes in plants beyond controlling root growth and nodule development [6,7,9,11]
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