Pollen differentiation as well as pollen tube guidance and discharge are independent of the presence of gametes [RESEARCH ARTICLE]

Barbara Glöckle, Wojciech J. Urban, Shiori Nagahara, Ellen D. Andersen, Tetsuya Higashiyama, Paul E. Grini, and Arp Schnittger

After meiosis, an unequal cell division generates the male gamete lineage in flowering plants. The generative cell will undergo a second division, giving rise to the two gametes, i.e. the sperm cells. The other cell will develop into the vegetative cell that plays a crucial role in pollen tube formation and sperm delivery. Recently, the vegetative cell has been implicated to be important for programming of the chromatin state in sperm cells and/or the resulting fertilization products. Blocking the initial unequal division genetically, we first highlight that the default differentiation state after male meiosis is a vegetative fate consistent with earlier work. We find that uni-nucleated mutant microspores differentiated as wildtype vegetative cells, including chromatin remodeling and the transcriptional activation of transposable elements. Moreover, live cell imaging revealed that this vegetative cell is sufficient for the correct guidance of the pollen tube to the female gametes. Hence, we conclude that vegetative cell differentiation and function does not depend on the formation or presence of the actual gametes but rather on external signals or a cell autonomous pace keeper.

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