College of Life and Environmental Sciences, Shanghai Normal University, 100 Guilin Road, Shanghai, 200234, China.
Institute of Plant and Food Science, Department of Biology, Southern University of Science and Technology, Shenzhen, Guangdong, 508055, China.
Plant J. 2018 Oct;96(1):176-187. doi: 10.1111/tpj.14027. Epub 2018 Aug 12.
ETHYLENE INSENSITIVE 3 (EIN3) is a key regulator of ethylene signaling, and EIN3-BINDING F-BOX1 (EBF1) and EBF2 are responsible for EIN3 degradation. Previous reports have shown that the ebf1 ebf2 double homozygous mutant cannot be identified. In this study, the genetic analysis revealed that the ebf1 ebf2 female gametophyte is defective. The pollination experiment showed that ebf1 ebf2 ovules failed to attract pollen tubes. In female gametophyte/ovule, the synergid cell is responsible for pollen tube attraction. Observation of the pEIN3::EIN3-GFP transgenic lines showed that EIN3 signal was over-accumulated at the micropylar end of ebf1 ebf2 female gametophyte. The overexpression of stabilized EIN3 in synergid cell led to the defect of pollen tube guidance. These results suggested that the over-accumulated EIN3 in ebf1 ebf2 synergid cell blocks its pollen tube attraction which leads to the failure of ebf1 ebf2 homozygous plant. We identified that EIN3 directly activated the expression of a sugar transporter, SENESCENCE-ASSOCIATED GENE29 (SAG29/SWEET15). Overexpression of SAG29 in synergid cells blocked pollen tube attraction, suggesting that SAG29 might play a role in ethylene signaling to repel pollen tube entry. Taken together, our study reveals that strict control of ethylene signaling is critical for the synergid cell function during plant reproduction.
乙烯不敏感 3（EIN3）是乙烯信号转导的关键调节因子，EIN3 结合 F 框 1（EBF1）和 EBF2 负责 EIN3 的降解。先前的报道表明，ebf1 ebf2 双纯合突变体无法被鉴定。在这项研究中，遗传学分析表明 ebf1 ebf2 雌性配子体有缺陷。授粉实验表明，ebf1 ebf2 胚珠无法吸引花粉管。在雌性配子体/胚珠中，助细胞负责吸引花粉管。观察 pEIN3::EIN3-GFP 转基因系表明，EIN3 信号在 ebf1 ebf2 雌性配子体的珠孔端过度积累。助细胞中稳定表达的 EIN3 过表达导致花粉管导向缺陷。这些结果表明，ebf1 ebf2 助细胞中过度积累的 EIN3 阻断了其对花粉管的吸引，导致 ebf1 ebf2 纯合植物的失败。我们鉴定出 EIN3 直接激活了糖转运蛋白 SENESCENCE-ASSOCIATED GENE29（SAG29/SWEET15）的表达。在助细胞中过表达 SAG29 阻断了花粉管的吸引，表明 SAG29 可能在乙烯信号转导中发挥作用，以排斥花粉管进入。总之，我们的研究揭示了严格控制乙烯信号对植物繁殖过程中助细胞功能的重要性。
