Description:
<jats:title>Abstract</jats:title><jats:sec><jats:title>Background</jats:title><jats:p>The pH is an important parameter controlling many metabolic and signalling pathways in living cells. Recombinant fluorescent pH indicators (pHluorins) have come into vogue for monitoring cellular pH. They are derived from the most popular<jats:italic>Aequorea victoria</jats:italic>GFP (<jats:italic>Av-</jats:italic>GFP). Here, we present a novel fluorescent pH reporter protein from the orange seapen<jats:italic>Ptilosarcus gurneyi</jats:italic>(<jats:italic>Pt-</jats:italic>GFP) and compare its properties with pHluorins for expression and use in plants.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>pHluorins have a higher pH-sensitivity. However,<jats:italic>Pt-</jats:italic>GFP has a broader pH-responsiveness, an excellent dynamic ratio range and a better acid stability. We demonstrate how<jats:italic>Pt</jats:italic>-GFP expressing<jats:italic>Arabidopsis thaliana</jats:italic>report cytosolic pH-clamp and changes of cytosolic pH in the response to anoxia and salt-stress.</jats:p></jats:sec><jats:sec><jats:title>Conclusion</jats:title><jats:p><jats:italic>Pt-</jats:italic>GFP appears to be the better choice when used for<jats:italic>in vivo-</jats:italic>recording of cellular pH in plants.</jats:p></jats:sec>