Involvement of the glycine-rich RNA-binding proteins (GRP) in plant abiotic stress response: a comparison between GRP 2 and GRP 7

Abstract

The plant glycine-rich RNA-binding proteins (GRP) are a major class of proteins known to be implicated in plant response to abiotic and biotic stress. Recent studies regarding this type of proteins focused mostly on two of them, namely GRP2 and GRP7, which are mainly involved in osmotic and oxidative plant adaptation mechanisms. The main purpose of this research was to assess the involvement of these two glycine-rich RNA-binding proteins (GRP2 and GRP7) in seed germination capacity under drought stress conditions using the model plant Arabidopsis thaliana. The plant material was composed out of seed batches obtained from the T-DNA insertion Arabidopsis thaliana mutant lines labelled grp2 (knock-out mutant for the glycine-rich RNA-binding protein 2), grp7-1 (knock-out mutant for the glycine-rich RNA-binding protein 7), and the ecotype Columbia 0 (Col0), which was used as control. For the germination assay, the control medium ½ MS (Murashige&Skoog) was supplemented with three different concentrations (100mM, 200mM and 300mM) of mannitol. The germination was assessed each day during one week. After this period, the germination rate was estimated. Three independent replicates were used and the statistical analysis, namely the ANOVA test, was made using the Graph Pad Prism software (trial version). We observed a difference between the two mutants: grp2 seeds germinated similarly on the control medium as well as on the medium supplemented with various mannitol concentrations, while grp7-1 seeds showed a poor germination rate on all three mannitol culture mediums. The germination rate of the grp2 seeds was also increased, on all the culture mediums used, in comparison to the control Col0 seeds. In the present research work, we demonstrated that even though the two proteins GRP2 and GRP7 belong to the same family, their implication in the seed germination capacity under drought stress is opposite, one enhancing the germination, while the other is reducing it.