PDLP5 regulates aquaporin-mediated hydrogen peroxide transport in Arabidopsis

Abstract

Aquaporins facilitate the diffusion of water and small neutral molecules, including hydrogen peroxide (H2O2). In Arabidopsis, plasma membrane intrinsic proteins (PIPs, members of aquaporins) mediate H2O2 transport; however, the regulatory mechanisms governing their activity are not fully understood. Here, we show that plasmodesmata-located protein 5 (PDLP5), a key regulator of plasmodesmal function, negatively regulates PIP-dependent H2O2 transport. PDLP5 forms complexes with PIPs, with its extracellular domain predicted to associate with the extracellular face of the channel. PDLP5 overexpression suppresses H2O2 uptake and confers reduced sensitivity to H2O2-induced root growth inhibition, whereas pdlp5 mutants display the opposite phenotype. We further identify PIP2;5 as a critical component of PDLP5-mediated regulation. These findings reveal an extracellular mechanism for modulating aquaporin function, expanding current models of channel regulation in plants.