Arabidopsis pollen-specific glycerophosphodiester phosphodiesterase-like genes are essential for pollen tube tip growth

In angiosperms, pollen tube growth is critical for double fertilization and seed formation. Many of the factors involved in pollen tube tip growth are unknown. Here, we report the roles of pollenspecific GLYCEROPHOSPHODIESTER PHOSPHO DIESTERASE-LIKE(GDPD-LIKE) genes in pollen tube tip growth. Arabidopsis thaliana GDPD-LIKE6(At GDPDL6) and At GDPDL7 were specifically expressed in mature pollen grains and pollen tubes and green fluorescent protein(GFP)-At GDPDL6 and GFP-At GDPDL7 fusion proteins were enriched at the plasma membrane at the apex of forming pollen tubes. Atgdpdl6 Atgdpdl7 double mutants displayed severe sterility that was rescued by genetic complementation with At GDPDL6 or At GDPDL7. This sterility was associated with defective male gametophytic transmission.Atgdpdl6 Atgdpdl7 pollen tubes burst immediately after initiation of pollen germination in vitro and in vivo, consistent with the thin and fragile walls in their tips. Cellulose deposition was greatly reduced along the mutant pollen tube tip walls, and the localization of pollen-specific CELLULOSE SYNTHASE-LIKE D1(CSLD1) and CSLD4 was impaired to the apex of mutant pollen tubes. A rice pollen-specific GDPD-LIKE protein also contributed to pollen tube tip growth, suggesting that members of this family have conserved functions in angiosperms. Thus, pollen-specific GDPDLIKEs mediate pollen tube tip growth, possibly by modulating cellulose deposition in pollen tube walls.