The LOTUS-domain containing protein PpLDCP3 controls germline and dispersal unit formation in the moss Physcomitrium patens

O_LIDispersal is crucial for the survival and thriving of plant populations, yet the mechanisms of dispersal unit formation are poorly understood. LOTUS domain-containing proteins are essential for animal reproduction, promoting cell cycle control, transposon silencing, and transgenerational inheritance in the germline. In this study, we demonstrate that the formation of dispersal units, sperm and spores, in the model moss Physcomitrium patens relies on the novel LOTUS domain-containing protein 3 (PpLDCP3). C_LIO_LIPpldcp3 knock-out mutants revealed pleiotropic phenotypes in both gametogenesis and sporogenesis. Ppldcp3 sperm were rarely released and appeared to be partially non-viable, leading to fewer sporophytes produced. Sporophyte development in Ppldcp3 was impaired, resulting in abnormal dehiscence of spores, which were incapable of germinating. C_LIO_LIFluorescent reporter lines revealed the presence of PpLDCP3 in developing gametangia. Within the premature egg cell and ventral canal cell of archegonia, PpLDCP3 was identified as a component of cytoplasmic fluorescent foci, which we interpret as P-bodies. This suggests a role for PpLDCP3 in RNA metabolism, analogous to animal LDCPs. Moreover, bioinformatic predictions indicate PpLDCP3 as a downstream player of WOX13 and bHLH transcription factors. C_LIO_LIWe conclude that PpLDCP3 is integrated into evolutionary conserved mechanisms of dispersal unit formation in land plants. C_LI