PIN-driven auxin transport emerged early in streptophyte evolution

PIN-FORMED (PIN) transporters mediate directional, intercellular movement of the phytohormone auxin in land plants. To elucidate the evolutionary origins of this developmentally crucial mechanism, we analysed the single PIN homologue of a simple green alga Klebsormidium flaccidum. KfPIN functions as a plasma membrane-localized auxin exporter in land plants and heterologous models. While its role in algae remains unclear, PIN-driven auxin export is probably an ancient and conserved trait within streptophytes. The authors studied the function of a PIN gene in a filamentous charophyte green alga (Klebsormidium flaccidum). They found that the plasma membrane auxin efflux function is an early trait that emerged before divergence between algae and land plants.