Arabidopsis thaliana Glycine Rich Ribosome Binding Protein 3 (AtGR-RBP3) is a Negative Regulator of Salinity Stress

Abstract

Salinity is one of the major abiotic stresses that affect crop production. Mechanism(s) of plant tolerance to salinity is complex and is mediated by multiple biochemical pathways. Our earlier studies have shown that Ascophyllum nodosum extracts (ANE) impart salinity tolerance in plants. To understand the molecular mechanism of salinity tolerance induced by ANE, the whole genome transcriptome of Arabidopsis thaliana was examined through microarray analysis. Analysis of the ANE-induced transcriptome under salinity stress led to the identification of a number of positive and negative regulators of salinity tolerance in Arabidopsis. I systematically screened Arabidopsis single gene knockout mutants corresponding to genes that were significantly down regulated in ANE-mediated salinity tolerance. In this study it was observed that plants carrying a mutation in the gene Arabidopsis thaliana Glycine Rich-Ribosome Binding Protein 3 (AtGR-RBP3) exhibited a marked salt tolerance compared to wild type Arabidopsis Col-0. AtGR-RBP3 mutants, gr-rbp3-1 and gr-rbp3-2, accumulated significantly less sodium (36 and 37.76 µg mg-1 of dry weight respectively) in their leaf tissue as compared wild type plants (57.73 µg mg-1) when grown under high salt conditions. Also, the increase in sodium:potassium (Na+/K+) ratio which was observed in wild type (7.0) was not observed in gr-rbp3-1 and gr-rbp3-2 (3.12 and 3.54 respectively). In this research an increase in the expression of stress responsive genes; RD29A, RD22 and SOS1 was evident in gr-rbp3-1 and gr-rbp3-2. Subcellular localization study revealed that ATGR-RBP3 was localized in the endoplasmic reticulum. Taken together, these results indicate that AtGR-RBP3 is a negative regulator of salinity stress in Arabidopsis.