Phytosphinganine Affects Plasmodesmata Permeability via Facilitating PDLP5-Stimulated Callose Accumulation in Arabidopsis

Abstract Plant plasmodesmata (PDs) are specialized channels that enable communication between neighboring cells. The intercellular permeability of PDs affecting plant development, defense and responses to stimulus must be tightly regulated. Analysis of specific PD membrane lipid composition and their impact on PD permeability will provide new insights into PD regulatory mechanism. Herein, we report that the Arabidopsis sld1 sld2 double mutant, lacking sphingolipid long-chain base 8 desaturases 1 and 2, displayed decreased PD permeability due to a significant increase in callose accumulation. Plasmodesmata-located protein 5 (PDLP5) was significantly enriched in the leaf epidermal cells of sld1 sld2 and showed specific binding affinity to phytosphinganine (t18:0), suggesting that the enrichment of t18:0-based sphingolipids in sld1 sld2 PDs might facilitate the recruitment of more PDLP5. The double mutants showed enhanced resistance to the fungal-wilt pathogen Verticillium dahlia or the bacterium Peudomonas syringae pv tomato DC3000. This phenotype was fully restored in sld1 sld2 pdlp5. Thus, we proposed that phytosphinganine might regulate PDs functions and cell-to-cell communication by modifying the level of PDLP5 in PD membranes.