Key Laboratory of Seed Innovation, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China.
Center for Molecular Agrobiology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China.
Nat Plants. 2024 Jun;10(6):1027-1038. doi: 10.1038/s41477-024-01703-1. Epub 2024 Jun 3.
In bryophytes, sexual reproduction necessitates the release of motile sperm cells from a gametophyte into the environment. Since 1856, this process, particularly in liverworts, has been known to depend on water. However, the molecular mechanism underlying this phenomenon has remained elusive. Here we identify the plasma membrane protein MpMLO1 in Marchantia polymorpha, a model liverwort, as critical for sperm discharge from antheridia. The MpMLO1-expressing tip cells among the sperm-wrapping jacket cells undergo programmed cell death upon antheridium maturation to facilitate sperm discharge after the application of water and even hypertonic solutions. The absence of MpMLO1 leads to reduced cytoplasmic Ca levels in tip cells, preventing cell death and consequently sperm discharge. Our findings reveal that MpMLO1-mediated programmed cell death in antheridial tip cells, regulated by cytosolic Ca dynamics, is essential for sperm release, elucidating a key mechanism in bryophyte sexual reproduction and providing insights into terrestrial plant evolution.
在苔藓植物中，有性生殖需要游动的精子细胞从配子体释放到环境中。自 1856 年以来，人们就知道这个过程（特别是在苔类植物中）依赖于水。然而，这一现象背后的分子机制仍然难以捉摸。在这里，我们鉴定了模式苔类植物 Marchantia polymorpha 中的质膜蛋白 MpMLO1 对于从藏精器中排出精子是至关重要的。在藏精器成熟后，MpMLO1 表达的顶端细胞在施加水甚至高渗溶液后会发生程序性细胞死亡，以促进精子排出。MpMLO1 的缺失导致顶端细胞中的细胞质 Ca 水平降低，阻止细胞死亡，从而阻止精子排出。我们的发现揭示了 MpMLO1 介导的藏精器顶端细胞程序性细胞死亡，受细胞质 Ca 动力学调控，对于精子释放是必不可少的，阐明了苔藓植物有性生殖的关键机制，并为陆地植物进化提供了新的见解。
