Mori Toshiyuki, Kuroiwa Haruko, Higashiyama Tetsuya, Kuroiwa Tsuneyoshi
Department of Life Science, College of Science, Rikkyo (St. Paul's) University, Nishiikebukuro 3-34-1, Toshima-ku, Tokyo 171-8501, Japan.
Nat Cell Biol. 2006 Jan;8(1):64-71. doi: 10.1038/ncb1345. Epub 2005 Dec 25.
The double fertilization process in angiosperms is based on the delivery of a pair of sperm cells by the pollen tube (the male gametophyte), which elongates towards an embryo sac (the female gametophyte) enclosing an egg and a central cell. Several studies have described the mechanisms of gametophyte interaction, and also the fertilization process - from pollination to pollen tube acceptance. However, the mechanisms of gamete interaction are not fully understood. Cytological studies have shown that male gametes possess distinct cell-surface structures and genes specific to male gametes have been detected in cDNA libraries. Thus, studies of isolated gametes may offer clues to understanding the sperm-egg interaction. In this study, we identified a novel protein, designated GCS1 (GENERATIVE CELL SPECIFIC 1), using generative cells isolated from Lilium longiflorum pollen. GCS1 possesses a carboxy-terminal transmembrane domain, and homologues are present in various species, including non-angiosperms. Immunological assays indicate that GCS1 is accumulated during late gametogenesis and is localized on the plasma membrane of generative cells. In addition, Arabidopsis thaliana GCS1 mutant gametes fail to fuse, resulting in male sterility and suggesting that GCS1 is a critical fertilization factor in angiosperms.
被子植物的双受精过程基于花粉管（雄配子体）输送一对精细胞，花粉管朝着包围着一个卵细胞和一个中央细胞的胚囊（雌配子体）伸长。多项研究描述了配子体相互作用的机制，以及从授粉到花粉管接受的受精过程。然而，配子相互作用的机制尚未完全了解。细胞学研究表明，雄配子具有独特的细胞表面结构，并且在cDNA文库中检测到了雄配子特有的基因。因此，对分离出的配子进行研究可能为理解精卵相互作用提供线索。在本研究中，我们利用从麝香百合花粉中分离出的生殖细胞鉴定出一种新蛋白，命名为GCS1（生殖细胞特异性蛋白1）。GCS1具有一个羧基末端跨膜结构域，并且在包括非被子植物在内的各种物种中都存在同源物。免疫分析表明，GCS1在配子发生后期积累，并定位于生殖细胞的质膜上。此外，拟南芥GCS1突变体配子无法融合，导致雄性不育，这表明GCS1是被子植物中的一个关键受精因子。
