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Pollen tube attraction by the synergid cell
Species name:Torenia fournieri
ITbM, Nagoya Univ Tetsuya Higashiyama
In the evolution of flowering plants, genes necessary for flagella formation including flagellar dyneins were lost. Non-motile sperm cells of flowering plants are conveyed by a tip-growing haploid cell, the pollen tube. The sperm cell is enclosed by an endocytic membrane of the pollen tube cell and delivered to female gametes rapidly without much water for swimming. How does the pollen tube precisely arrive at an egg-containing tissue? Pollen tube attractants had been searched for more than 140 years. The attractants were finally identified in a unique plant species, Torenia, which has a protruding egg-containing tissue. Pollen tube attraction can be directly observed in Torenia as shown in this movie. Two synergid cells on the side of the egg cell were shown to be the source of the attraction signal. Finally, two cysteine-rich peptides named LUREs were identified as true pollen tube attractants.