Overexpression of SaARF gene, an Adenosine Diphosphate-Ribosylation Factor from Spartina alterniflora, Confers Enhanced Osmotic Stress Tolerance in Arabidopsis

Abiotic stresses such as salinity, drought, and extreme temperature adversely affect plant growth and development. Although several groups of abiotic stress related genes based on gene ontology have been identified in plants, the biological functions of many of these genes are still largely unknown. In this direction, identification and characterization of genes from a halophytic plant Spartina alterniflora is promising due to its natural tolerance to salinity. Previously, we have identified a number of salinity responsive genes in Spartina alterniflora, whose functions are being validated to understand their role in abiotic stress tolerance. In this study, we have characterized an adenosine diphosphate ribosylation factor (ARF) from Spartina alterniflora designated as SaARF. SaARF encoded a 20 KD protein with a calculated isoelectric point of 6.43. SaARF protein had many characteristic features as reported in other ARF proteins, such as GTP binding domain and effector domain. Amino acid sequence comparison revealed higher homology of SaARF with ARF of monocots as well as dicots. SaARF gene was found to be differentially regulated by salinity, dehydration, low temperature and ABA in the leaves and roots of Spartina alterniflora. Further, to understand the function of SaARF towards stress tolerance in plants, SaARF was constitutively expressed in model plant Arabidopsis. SaARF expressing Arabidopsis plants showed improved tolerance to osmotic stress than the wild type possibly by minimizing the oxidative damage of leaf tissues caused by reactive oxygen species through regulation of stress responsive genes. SaARF can be a potential candidate gene for improving abiotic stress tolerance in crop plants.