College of Life Sciences, Hunan Normal University, Changsha 410081, People's Republic of China.
Proc Natl Acad Sci U S A. 2010 Dec 21;107(51):22332-7. doi: 10.1073/pnas.1015911107. Epub 2010 Dec 1.
Double fertilization in angiosperms involves several successive steps, including guidance and reception of the pollen tube and male-female gamete recognition. Each step entails extensive communication and interaction between two different reproductive cell or tissue types. Extensive research has focused on the pollen tube, namely, its interaction with the stigma and reception by maternal cells. Little is known, however, about the mechanism by which the gametes recognize each other and interact to form a zygote. We report that an ankyrin repeat protein (ANK6) is essential for fertilization, specifically for gamete recognition. ANK6 (At5g61230) was highly expressed in the male and female gametophytes before and during but not after fertilization. Genetic analysis of a T-DNA insertional mutant suggested that loss of function of ANK6 results in embryonic lethality. Moreover, male-female gamete recognition was found to be impaired only when an ank6 male gamete reached an ank6 female gamete, thereby preventing formation of homozygous zygotes. ANK6 was localized to the mitochondria, where it interacted with SIG5, a transcription initiation factor previously found to be essential for fertility. These results show that ANK6 plays a central role in male-female gamete recognition, possibly by regulating mitochondrial gene expression.
被子植物的双受精涉及几个连续的步骤，包括花粉管的引导和接收以及雌雄配子的识别。每个步骤都需要两种不同的生殖细胞或组织类型之间进行广泛的交流和相互作用。大量的研究集中在花粉管上，即花粉管与柱头的相互作用以及被母体细胞接收。然而，对于配子如何相互识别并相互作用形成受精卵的机制知之甚少。我们报告说，锚蛋白重复蛋白（ANK6）是受精所必需的，特别是对配子识别是必需的。ANK6（At5g61230）在受精前后的雄性和雌性配子体中高度表达，但受精后不表达。T-DNA 插入突变体的遗传分析表明，ANK6 功能丧失会导致胚胎致死。此外，只有当 ank6 雄性配子与 ank6 雌性配子相遇时，才会发现雌雄配子识别受损，从而阻止纯合子受精卵的形成。ANK6 定位于线粒体，与 SIG5 相互作用，SIG5 是先前发现对生育至关重要的转录起始因子。这些结果表明，ANK6 在雌雄配子识别中发挥核心作用，可能通过调节线粒体基因表达。
