Evolutionary appearance of the plasma membrane H+-ATPase containing a penultimate threonine in the bryophyte

Abstract

The plasma membrane H+-ATPase provides the driving force for solute transport via an electrochemical gradient of H+ across the plasma membrane, and regulates ph homeostasis and membrane potential in plant cells. however, the plasma membrane H+-ATPase in non-vascular plant bryophyte is largely unknown. here, we show that the moss Physcomitrella patens, which is known as a model bryophyte, expresses both the penultimate thr-containing H±-ATPase (pt H+-ATPase) and non-pT H+-ATPase as in the green algae, and that pT H+-ATPase is regulated by phosphorylation of its penultimate Thr. A search in the P. patens genome database revealed seven H+-ATPase genes, designated PpHA (Physcomitrella patens H+-ATPase). Six isoforms are the pT H+-ATPase; a remaining isoform is non-pT H+-ATPase. An apparent 95-kD protein was recognized by anti-H+-ATPase antibodies against an isoform of Arabidopsis thaliana and was phosphorylated on the penultimate thr in response to a fungal toxin fusicoccin and light in protonemata, indicating that the 95-kD protein contains pT H+-ATPase. Furthermore, we could not detect the pT H+-ATPase in the charophyte alga Chara braunii, which is the closest relative of the land plants, by immunological methods. these results strongly suggest the pT H+-ATPase most likely appeared for the first time in bryophyte. © 2012 Landes Bioscience.