Abstract
In higher plants, the double-fertilization process begins with the successful delivery of two sperm cells to the female gametophyte. The sperms cells are carried by a pollen tube that upon arrival at the micropylar end of the female gametophyte, bursts, and discharges its content into one of two specialized cells called the synergid cells. At their micropylar ends, both synergid cells form a thickened cell wall with a unique structure called the filiform apparatus. The filiform apparatus is believed to play a major role in pollen tube guidance and reception. It has also been assumed that the pollen tube enters the receptive synergid cell through the filiform apparatus. Here, we show that in Arabidopsis ovules, the arriving pollen tube appears to grow beyond the filiform apparatus to enter the synergid cell at a more distant site, where the tube bursts to release its contents. Thus, fertilization in Arabidopsis might involve two spatially and temporally separable stages, recognition and entry, with the latter apparently not requiring the filiform apparatus.
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Acknowledgments
The authors are grateful to Aneesh Panoli for his useful comments and helpful discussions and to Ravi Palanivelu for the LAT52::DsRed line. This research was supported by a National Science Foundation grant IOS-1051951 to V.S. Y.L. was partially supported by a Vaadia-BARD Postdoctoral Fellowship Award FI-392-07 from BARD, the U.S.–Israel Binational Agricultural Research and Development Fund.
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Communicated by Dolf Weijers.
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Leshem, Y., Johnson, C. & Sundaresan, V. Pollen tube entry into the synergid cell of Arabidopsis is observed at a site distinct from the filiform apparatus. Plant Reprod 26, 93–99 (2013). https://doi.org/10.1007/s00497-013-0211-1
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DOI: https://doi.org/10.1007/s00497-013-0211-1