Abstract
Proteins with glycine-rich signatures have been reported in a wide variety of organisms including plants, mammalians, fungi, and bacteria. Plant glycine-rich protein genes exhibit developmental and tissue-specific expression patterns. Herein, we present the characterization of the AtGRDP2 gene using Arabidopsis null and knockdown mutants and, Arabidopsis and lettuce over-expression lines. AtGRDP2 encodes a short glycine-rich domain protein, containing a DUF1399 domain and a putative RNA recognition motif (RRM). AtGRDP2 transcript is mainly expressed in Arabidopsis floral organs, and its deregulation in Arabidopsis Atgrdp2 mutants and 35S::AtGRDP2 over-expression lines produces alterations in development. The 35S::AtGRDP2 over-expression lines grow faster than the WT, while the Atgrdp2 mutants have a delay in growth and development. The over-expression lines accumulate higher levels of indole-3-acetic acid and, have alterations in the expression pattern of ARF6, ARF8, and miR167 regulators of floral development and auxin signaling. Under salt stress conditions, 35S::AtGRDP2 over-expression lines displayed higher tolerance and increased expression of stress marker genes. Likewise, transgenic lettuce plants over-expressing the AtGRDP2 gene manifest increased growth rate and early flowering time. Our data reveal an important role for AtGRDP2 in Arabidopsis development and stress response, and suggest a connection between AtGRDP2 and auxin signaling.
Highlights
Glycine-rich proteins (GRPs) are characterized by a high content of glycine (40–70%) and repetitive sequence of residues arranged in (Gly)n-X motifs (Sachetto-Martins et al, 2000; Mousavi and Hotta, 2005)
The AtGRDP2 (At4g37900) gene is located in chromosome 4, and its genomic organization consists of five exons and four introns
The AtGRDP2 cDNA is 2428 bp in length containing an open reading frame (ORF) of 2364 pb that encodes a protein of 787 aa
Summary
Glycine-rich proteins (GRPs) are characterized by a high content of glycine (40–70%) and repetitive sequence of residues arranged in (Gly)n-X motifs (Sachetto-Martins et al, 2000; Mousavi and Hotta, 2005). Five groups have been suggested, according to the arrangement of the repeated glycine signatures as well as the presence of conserved motifs and domains (SachettoMartins et al, 2000; Mangeon et al, 2010). The group IV is based on the presence of additional motifs and domains such as RNA recognition motif (RRM), cold shock and zinc finger domains, and a cysteine-rich domain, among others (Bocca et al, 2005; Mangeon et al, 2010). Few plant GRPs have been characterized; these proteins appear to play important roles in transcriptional regulation, signal transduction, protein-protein interaction, development, and stress responses (Bocca et al, 2005)
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