PgPAP18, a heat-inducible novel purple acid phosphatase 18-like gene (PgPAP18-like) from Pennisetum glaucum, may play a crucial role in environmental stress adaptation

Purple acid phosphatases (PAPs) are ubiquitously present in plants, but their functional roles are still elusive. In this study, we isolated a novel full-length Pennisetum glaucum purple acid phosphatase 18-like (PgPAP18-like) gene, from pearl millet. PgPAP18 cDNA comprises 1410 bp and it encodes 469 amino acids including signal peptide. Insilico analysis of PgPAP18 emphasized that it belongs to metallo-phosphatase superfamily with di-nuclear (Fe-Zn) metal center. The gene further cloned into pET-28a (+) vector for protein expression and the purified recombinant protein showed phosphatase activity with para nitro phenyl phosphate (102 U mg(-1)). SDS-PAGE analysis revealed its molecular size of approximately 52.5 kDa and estimated isoelectric point (PI) as 6.21. The functional role of PgPAP18 in Escherichia coli augments the tolerance against (10%) of heat, (9%) of salt, (8.5%) of PEG, and (7%) of (CuSO4). pPICZ A-PAP18 recombinant clone expressed yeast cells were also affirmed E. coli stress tolerance. Spatial and temporal expression of Pennisetum leaf PAP18 transcript was significantly accumulated after 24 h of heat induction. The substantial changing expression level of PgPAP18 under heat treatment suggested that PgPAP18 may play crucial role in the accumulation of PAP18 under heat stress. Results indicated that PgPAP18 may play defensive role against environmental stresses and confer stress adaptation to the stress-tolerant plant. To the best of our best knowledge, the PgPAP18 gene isolation and recombinant protein purification from Pennisetum are first time described here which may play a critical role in abiotic stress tolerance in addition to phosphatase activity.