Structural Characterization of Cyclophilin A-like Protein from Piriformospora Indica & its Functional Validation in Salt Stress Tolerance

	Piriformospora indica, a plant-root-colonizing basidiomycete fungus, was discovered in the Indian Thar desert and has been shown to provide strong growth-promoting activity during its symbiosis with a broad spectrum of plants. We have found around 30 genes upregulated in P. indica under high salinity stress. One of the gene is Cyclophilin, which is widely distributed both in eukaryotes and prokaryotes and have a primary role as peptidyl-prolyl cis–trans isomerases (PPIases). We reported sequence-specific 1H, 13C and 15N resonance assignments for this Cyclophilin A like protein from P. indica by NMR spectroscopy. Structural analysis was also done by X-ray crystallography. In X-ray crystallography, crystals diffracted at 1.9 Å resolution and structure solution was carried out using Molecular Replacement method. This is the first study in which structure of a protein from P. indica fungus is determined at atomic-resolution. We have also demonstrated for the first time a direct evidence of countering salinity stress tolerance in plant by genetic modification using a P. indica gene. A novel RNA binding activity of PiCypA was also observed that might be part of machinery involved in RNA stabilization during stress conditions. We have also provided a direct evidence for a novel function of the Cyp A gene of P. indica  in high salinity (NaCl) stress tolerance in bacteria (E. coli). In order to study the role of the fungus gene (Cyp A) in salinity stress tolerance in plant, we have also raised Cyp A overexpressing tobacco transgenic plants. This study also provides an evidence for the role of P. indica Cyp A gene in salinity stress signalling. Further we have also analysed these transgenic by biochemical assays. The functional validation of PiCypA under salinity stress tolerance by plant applicable in agricultural crop advancements. These findings open up new areas for investigating the cellular machinery in plants and fungus to counteract salt stress tolerance and have a great potential for crop improvement.