PDLP5 regulates aquaporin-mediated hydrogen peroxide transport in Arabidopsis

Aquaporins facilitate the diffusion of water and small neutral molecules, including hydrogen peroxide (H 2 O 2 ). In Arabidopsis , plasma membrane intrinsic proteins (PIPs, members of aquaporins) mediate H 2 O 2 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 H 2 O 2 transport. PDLP5 forms complexes with PIPs, with its extracellular domain predicted to associate with the extracellular face of the channel. PDLP5 overexpression suppresses H 2 O 2 uptake and confers reduced sensitivity to H 2 O 2 -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.