On the cellular site of two‐pore channel <scp>TPC</scp>1 action in the Poaceae

<jats:title>Summary</jats:title><jats:p> <jats:list list-type="bullet"> <jats:list-item><jats:p>The slow vacuolar (<jats:styled-content style="fixed-case">SV</jats:styled-content>) channel has been characterized in different dicots by patch‐clamp recordings. This channel represents the major cation conductance of the largest organelle in most plant cells. Studies with the <jats:italic>tpc1‐2</jats:italic> mutant of the model dicot plant <jats:italic>Arabidopsis thaliana</jats:italic> identified the <jats:styled-content style="fixed-case">SV</jats:styled-content> channel as the product of the <jats:italic><jats:styled-content style="fixed-case">TPC</jats:styled-content>1</jats:italic> gene. By contrast, research on rice and wheat <jats:styled-content style="fixed-case">TPC</jats:styled-content>1 suggested that the monocot gene encodes a plasma membrane calcium‐permeable channel.</jats:p></jats:list-item> <jats:list-item><jats:p>To explore the site of action of grass <jats:styled-content style="fixed-case">TPC</jats:styled-content>1 channels, we expressed <jats:italic>Os<jats:styled-content style="fixed-case">TPC</jats:styled-content>1</jats:italic> from rice (<jats:italic>Oryza sativa)</jats:italic> and <jats:italic>Ta<jats:styled-content style="fixed-case">TPC</jats:styled-content>1</jats:italic> from wheat (<jats:italic>Triticum aestivum)</jats:italic> in the background of the <jats:italic>Arabidopsis tpc1‐2</jats:italic> mutant. Cross‐species <jats:italic>tpc1</jats:italic> complementation and patch‐clamping of vacuoles using <jats:italic>Arabidopsis</jats:italic> and rice <jats:italic>tpc1</jats:italic> null mutants documented that both monocot <jats:italic><jats:styled-content style="fixed-case">TPC</jats:styled-content>1</jats:italic> genes were capable of rescuing the <jats:styled-content style="fixed-case">SV</jats:styled-content> channel deficit.</jats:p></jats:list-item> <jats:list-item><jats:p>Vacuoles from wild‐type rice but not the <jats:italic>tpc1</jats:italic> loss‐of‐function mutant harbor <jats:styled-content style="fixed-case">SV</jats:styled-content> channels exhibiting the hallmark properties of dicot <jats:styled-content style="fixed-case">TPC</jats:styled-content>1/<jats:styled-content style="fixed-case">SV</jats:styled-content> channels. When expressed in human embryonic kidney (<jats:styled-content style="fixed-case">HEK</jats:styled-content>293) cells Os<jats:styled-content style="fixed-case">TPC</jats:styled-content>1 was targeted to Lysotracker‐Red‐positive organelles.</jats:p></jats:list-item> <jats:list-item><jats:p>The finding that the rice <jats:styled-content style="fixed-case">TPC</jats:styled-content>1, just like those from the model plant Arabidopsis and even animal cells, is localized and active in lyso‐vacuolar membranes associates this cation channel species with endomembrane function.</jats:p></jats:list-item> </jats:list> </jats:p>