Analysis of seven putative Na+/H+ antiporters of Arthrospira platensis NIES-39 using transcription profiling and in silico studies: an indication towards alkaline pH acclimation

Abstract

Na+/H+ antiporters mediated pH regulation is one of the known mechanism(s), which advocates a possible role of the antiporters in the alkaline pH tolerance of Arthrospira platensis NIES-39. Seven putative Na+/H+ antiporters have been reported in A. platensis NIES-39. Based upon the in silico analysis, the seven putative antiporters were characterized into two different superfamilies, where A1, Q2, L2, and L6 belonged to the CPA1 family whereas C5, D5 and O6 belonged to CPA2 family. The orientation of functionally important residues in both CPA1 and CPA2 subfamily are conserved in modeled Q2 and C5 antiporters. Conserved domain analysis of the seven putative antiporters indicated the presence of nine different kinds of domains. Out of these nine domains, six domains function as monovalent cation-proton antiporters and two as the universal stress protein (Usp) category. Transcription profile of these seven antiporters was also generated at three different pH (7, 9 and 11) and time frames which showed a significant difference in the mRNA levels along with a temporal pattern of the expression profile. The in silico and the real-time PCR analysis put together, suggest the active participation of these seven putative Na+/H+ antiporters in alkaline pH homeostasis of this cyanobacterial strain where CPA1 subfamily antiporters play a major role.