Molecular cloning and characterisation of a germin-like protein gene in spinach (SoGLP)

Germin-like proteins (GLPs) are ubiquitous plant glycoproteins that have been implicated in various plant physiological and developmental processes. In this study, a cDNA clone, designated SoGLP, encoding a germin-like protein from spinach (Spinacia oleracia L.) was isolated and characterised. SoGLP encodes a 208-amino-acid polypeptide with a predicted molecular mass of 22.54 kDa and a pI of 5.95. Phylogenetic analysis indicated that SoGLP belonged to sub-family 3 of the GLP family. Sub-cellular localisation of an SoGLP-GFP fusion protein appeared to detect the protein on the cell walls in transgenic tobacco plants. Real-time quantitative RT-PCR analysis showed that the level of expression of SoGLP in the salt-resistant spinach cultivar ('Chaoji') was generally higher than in the salt-sensitive spinach cultivar ('Daye') grown in 160 mM nitrate ions for 0.5, 3.0, or 6.0 h. Expression of the SoGLP gene was also induced by other abiotic stresses including polyethylene glycol (PEG), NaCl, salicylic acid (SA), or H2O2 treatment. Our results indicate that SoGLP could play important roles during high nitrate stress or under other abiotic stresses.