Gametophytic pollen tube guidance
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The concept of a pollen tube attractant was proposed in the late nineteenth century when pollen tubes were found to grow toward excised pistil tissues on medium. Since then, for about 140 years, plant biologists have tried to identify the pollen tube attractants. However, no molecule has been convincingly demonstrated to be the true attractant that actually controls the navigation of pollen tubes in the pistil. The past decade has seen substantial progress in this field in terms of our understanding of the various mechanisms of pollen tube guidance. It was suggested that diffusible pollen tube attractants might provide localized signals that affect the directional growth of the pollen tube, especially in the last phase of guidance by the target female gametophyte. Here, we review the mechanisms of pollen tube guidance, with special focus on the gametophytic guidance and the attractant. The necessary and appropriate conditions required by the true attractant will be discussed.
KeywordsPollen tube guidance Attractant Synergid cell
Our work on pollen tube guidance is supported by the Ministry of Education, Culture, Sports, Science and Technology, Japan (grant-in-aid for scientific research on priority areas no. 18075004, grant-in-aid for Scientific Research (B) no. 19370017, and PRESTO to T.H.).
Movie S1. See text and the legend of Fig.2 for details. This movie is 64 times faster than the normal speed. (MOV 25.1 mb)
Movie S2. See text and the legend of Fig.3 for details. This movie is 64 times faster than the normal speed. (MOV 17.8 mb)
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