Functional Conservation of the DDP1-type Inositol\nPyrophosphate Phosphohydrolases in Land Plant

Inositol\npyrophosphates (PP-InsPs) are eukaryote-specific second\nmessengers that regulate diverse cellular processes, including immunity,\nnutrient sensing, and hormone signaling pathways in plants. These\nenergy-rich messengers exhibit high sensitivity to the cellular phosphate\nstatus, suggesting that the synthesis and degradation of PP-InsPs\nare tightly controlled within the cells. Notably, the molecular basis\nof PP-InsP hydrolysis in plants remains largely unexplored. In this\nstudy, we report the functional characterization of MpDDP1, a diadenosine\nand diphosphoinositol polyphosphate phosphohydrolase encoded by the\ngenome of the liverwort, Marchantia polymorpha. We show that MpDDP1 functions as a PP-InsP phosphohydrolase in\ndifferent heterologous organisms. Consistent with this finding, M. polymorpha plants defective in MpDDP1 exhibit\nelevated levels of 1/3-InsP<sub>7</sub> and 1/3,5-InsP<sub>8</sub>, highlighting the contribution of MpDDP1 in regulating PP-InsP homeostasis <i>in planta</i>. Furthermore, our study reveals that MpDDP1 controls\nthallus development and vegetative reproduction in M. polymorpha. Collectively, this study provides\ninsights into the regulation of specific PP-InsP messengers by DDP1-type\nphosphohydrolases in land plants.