Computational study of sucrose non-fermenting 1-related kinase 2 (SnRK2): An in-silico approach for homology modelling and structural characterization of drought related SAPK9 gene in rice (Oryza sativa L.)

Sucrose non-fermenting-1-related protein kinase 2 (SnRK2) are plant-specific serine/threonine (Ser/Thr) protein kinases that form the central region of abscisic acid (ABA) signaling pathways and are major contributors in imparting abiotic stress tolerance in plants by activating protein phosphorylation pathways. SAPK9 (member of the SnRK2 family) plays a role in providing drought tolerance in rice but scanty literature is available related to its structural and physico-chemical characterization. Hence, the present study aimed at in-silico characterization and structural modelling of SAPK9 from Oryza sativa japonica (OsjSAPK9). The results revealed that OsjSAPK9 is highly conserved at the amino acid sequence level. A single Ser/Thr kinase domain along with ATP binding domain was found in OsjSAPK9. It is 361 amino acid residues long having 40 kDa molecular weight and 4.81 pI. All SnRK2 proteins are stable in nature (instability index > 40). 11 motifs were identified where motif 1 represents the SnRK2 domain. All SnRK2s were found to be localized in the nucleus. The larger number of phosphorylation sites for serine and threonine as compared to tyrosine and 10 antigenic determinant sites were observed. The structure showed 7-& beta;-strands, 15-& alpha;-helices, 39-& beta;-turns, 18-& gamma;-turns, and 4-beta hairpins. ATP was found to be a preferred ligand for OsjSAPK9. SAPK9 was found to interact with BZIP46 and BZIP23 transcription factors which behave as positive modulators of drought stress resistance. As SAPK9 protein plays a crucial role in ABA and stress signaling pathways, a deeper knowledge of its structural and functional attributes will open up new avenues for future research to strengthen rice's ability to withstand drought stress.