721 / 2019-05-09 14:46:19

Pollen Tube Guidance in Flowering Plants: The Interplay between Male and Female Gametophytes

Gametophyte, pollen, pollen tube guidance, Arabidopsis

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During evolution, novel reproductive structures and mechanisms have evolved to adapt to terrestrial land environment in plants. In angiosperms, this is manifested by the flower, multicellular gametophyte, double fertilization and siphonogamy in which the immotile sperm was delivered to the egg by a pollen tube produced by pollen. The tube growth is a guided process (PTG) that requires the intimate interactions between the pollen tube and maternal tissue of the pistil and the female gametophyte respectively. Through genetic screen, a number of genes were identified. CCG, a central cell-specifically expressed gene, is required for the female gametophyte to attract the pollen tube. CCG encodes a nuclear protein that regulates the expression of a number genes important for PTG via CBP1 which interacts with RNA polymerase II, the Mediator complex and AGL transcription factors in the central cells and also LURE1 expression in the synergid indirectly. POD1, a pollen tube-expressed gene, is required for the male gametophyte to respond to the female signals. POD1 encodes a ER protein that interact specifically with CRT3 which is implicated to control the folding of LRR-RLKs. Recently, two LRR-RLKs were identified as LURE1 receptor. These findings provide novel insight to mechanisms controlling PTG, but the molecular mechanisms and signaling pathways control pollen tube growth are not yet clear.