The female germ unit is essential for pollen tube funicular guidance in Arabidopsis thaliana

In angiosperm, two immotile sperm cells are delivered to the female gametes for fertilization by a pollen tube, which perceives guidance cues from ovules at least at two critical sites, micropyle for short-distance guidance and funiculus for comparably longer distance guidance. Compared with the great progress in understanding pollen tube micropylar guidance, little is known about the signaling for funicular guidance.Here, we show that funiculus plays an important role in pollen tube guidance and report that female gametophyte (FG) plays a critical role in funicular guidance by analysis of a 3-dehydroquinate synthase (DHQS) mutant. Loss function of DHQS in FG interrupts pollen tube funicular guidance, suggesting that the guiding signal is generated from FG.We show the evidence that the capacity of funicular guidance is established during FG functional specification after the establishment of cell identity. Specific expression of DHQS in the synergid cells, central cells, or egg cells can rescue funicular guidance defect in dhqs/+, indicating all the female germ unit cells are involved in the funicular guidance.The finding reveals that the attracting signal of pollen tube funicular guidance was generated at a site and stage manner and provides novel clue to locate and search for the signal.

Automated summary

In angiosperm, the ovules provide guidance cues for pollen tube fertilization, with the micropyle guiding the tube over short distances and the funiculus guiding it over longer distances. However, little is known about the signaling for funicular guidance. In this study, the researchers discovered that the funiculus and the female gametophyte play important roles in pollen tube guidance, with the loss of a specific gene interrupting funicular guidance. Furthermore, they found that the guiding signal for funicular guidance is generated from the female gametophyte and that all the female germ unit cells are involved in funicular guidance.