AlSRG1, a novel gene encoding an RRM-type RNA-binding protein (RBP) from Aeluropus littoralis, confers salt and drought tolerance in transgenic tobacco

We characterized a novel stress tolerance gene from Aeluropus littoralis encoding a protein designed as AlSRG1 (A. littoralisStress-Related Gene 1). Phylogenetic and conserved domain prediction identified AlSRG1 as an uncharacterized protein of unknown function. The conserved domain database revealed that AlSRG1 contains an RNA-recognition motif (RRM). This domain was highlighted in AlSRG1 primary, secondary and tertiary structures with the two conserved motifs RNP1 and RNP2 being part of it. These two conserved motifs contain the active site for RNA-binding and a 3D-model of conserved domain (AlSRG1p) was built from known X-ray structures and sequence alignments. The analysis with RT-qPCR revealed higher AlSRG1 transcript accumulation under salt and osmotic stresses. Overexpression of AlSRG1 in transgenic tobacco plants improved both salt and osmotic tolerance and was accompanied by higher seedling survival rates, better growth parameters and ROS accumulation than non-transgenic plants (NT). Furthermore, the transgenic tobacco plants were able to complete their life cycle and to produce viable seeds while the NT plants died at the vegetative stage. The AlSRG1 transgenic lines compared to NT tobacco, showed a significantly lower water loss rate in senescent-basal leaves. AlSRG1 overexpression also enhanced the transcript levels of ROS-scavenging genes and some stress-related transcription factors under salt and osmotic stresses. Taken together, these results show that AlSRG1 may play an important positive modulation role in abiotic stress tolerance.