Zm908p11, encoded by a short open reading frame (sORF) gene, functions in pollen tube growth as a profilin ligand in maize

Abstract

Double fertilization of flowering plants depends on the targeted transportation of sperm to the embryo sac by the pollen tube. Currently, little is known about the underlying molecular mechanisms that regulate pollen germination and pollen tube growth in maize (Zea mays). Here, a maize pollen-predominant gene Zm908, with several putative short open reading frames (sORFs), was isolated and characterized. The longest ORF of Zm908 encodes a small protein of 97 amino acids. This was designated as Zm908p11 and is distributed throughout the maize pollen tube. Western blot detected the small peptide in mature pollen. Quantitative reverse transcription–PCR and northern blot analysis revealed that Zm908p11 was expressed predominantly in mature pollen grains. Ectopic overexpression of full-length Zm908 and Zm908p11 in tobacco resulted in defective pollen, while transgenic tobacco plants with a site-specific mutation or a frameshift mutation of Zm908p11 showed normal pollen development. Overexpression of Zm908p11 in maize decreased pollen germination efficiency. Maize pollen cDNA library screening and protein–protein interaction assays demonstrated that Zm908p11 interacts with maize profilin 1 (ZmPRO1). A microarray analysis identified 273 up-regulated and 203 down-regulated genes in the overexpressing transgenic Zm908p11 pollen. Taken together, these results indicate that Zm908 functions as Zm908p11, and binds to profilins as a novel ligand, with a required role during pollen tube growth in maize. Accordingly, a model is proposed for the role of Zm908p11 during pollen tube growth in maize.

Comprehensive Peptide Analysis of Mouse Brain Striatum Identifies Novel sORF‐Encoded Polypeptides

“…The first SEP was discovered in a plant in 1996, a 10 AA peptide expressed from ENOD40 transcript . This was soon followed by more identifications in plants including 36 aa peptide encoded from the POLARIS gene ( Arabidopsis thaliana ), ROTUNDIFOLIA4, Brick, Zm401, and Zm908p11 …”

Identification and characterization of sORF-encoded polypeptides

“…Unlike classical peptide hormones and neuropeptides, which are translated as larger precursor proteins followed by limited proteolytic processing (Holst, 2007, Steiner, 1998), these s(m)ORF-encoded polypeptides (SEPs) are short peptides encoded directly from s(m)ORFs (Galindo et al, 2007, Kondo et al, 2010, Magny et al, 2013, Pauli et al, 2014). A small number of well-studied SEPs have indicated that these polypeptides may act as important regulators in many fundamental biological processes, such as metabolism (Dong et al, 2013), development (Kondo et al, 2010, Pauli et al, 2014), and cell death (Hashimoto et al, 2001), but little is known about the biological activities, regulation, or even total number of SEPs. Therefore, discovery and functional characterization of SEPs will expand our knowledge of the composition of the genome and proteome, and provide fundamental insights into the molecular biology of cells.…”

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

“…Currently, six functionally characterized plant sPEPs encoded by transcripts not encoding longer proteins have been reported in the literature, namely, POLARIS (PLS; 36 amino acids), EARLY NODULIN GENE 40 (ENOD40;12,13,24, or 27 amino acids), ROTUNDIFOLIA FOUR (ROT4; 53 amino acids), KISS OF DEATH (KOD; 25 amino acids), BRICK1 (BRK1; 84 amino acids), Zm-908p11 (97 amino acids), and Zm-401p10 (89 amino acids) Dong et al, 2013;Crappé et al, 2013;Andrews and Rothnagel, 2014). However, based on the TAIR10 annotation of the Arabidopsis genome, 131 functionally annotated peptides (<100 amino acids) without an NSS can be identified.…”