动物：Upon gamete fusion, animal egg cells secrete proteases from cortical granules to establish a fertilization envelope as a block to polyspermy. 

植物：Fertilization in flowering plants is more complex and involves the delivery of two non-motile sperm cells by pollen tubes. Simultaneous penetration of ovules by multiple pollen tubes (polytubey) is usually avoided, thus indirectly preventing polyspermy. 

提出问题：How plant egg cells regulate the rejection of extra tubes after successful fertilization is not known.

主要发现：Here we report that the aspartic endopeptidases ECS1 and ECS2 are secreted to the extracellular space from a cortical network located at the apical domain of the Arabidopsis egg cell. This reaction is triggered only after successful fertilization.

结果2-表达模式：ECS1 and ECS2 are exclusively expressed in the egg cell and transcripts are degraded immediately after gamete fusion. 

结果3-功能：ECS1 and ESC2 specifically cleave the pollen tube attractor LURE1. 

结果4-突变体：As a consequence, polytubey is frequent in ecs1 ecs2 double mutants. 

结果5-异位表达：Ectopic secretion of these endopeptidases from synergid cells led to a decrease in the levels of LURE1 and reduced the rate of pollen tube attraction. 

结论：Together, these findings demonstrate that plant egg cells sense successful fertilization and elucidate a mechanism as to how a relatively fast post-fertilization block to polytubey is established by fertilization-induced degradation of attraction factors.

 摘 要 

一旦配子融合之后，动物的卵细胞会从皮质颗粒中分泌蛋白酶，形成受精膜，阻止多精子受精。有花植物中，受精作用更加复杂，通过花粉管递送两个本身不具活动能力的精子。有花植物通常会避免出现多个花粉管同时穿透胚珠的情况，从而间接地阻止了多精子受精的发生。但是，植物卵细胞如何调控在成功受精后阻断其它花粉管的还不清楚。本文中，作者发现在拟南芥中，位于卵细胞顶端区域的皮质网络会分泌两个天冬氨酸内肽酶ECS1和ECS2到胞外空间。该过程仅在卵细胞成功受精之后，才会被诱导、发生。ECS1和ECS2基因特异性在卵细胞中表达，并且其转录本会在配子融合后立马被降解。ECS1和ECS2会特异性剪切花粉管吸引子LURE1。因此，ecs1 ecs2双突植株中频繁出现多个花粉管现象。助细胞异位分泌这些天冬氨酸内肽酶会导致LURE1的水平降低，并且减少花粉管吸引率。综上，本文的研究揭示了植物卵细胞能够感知受精成功，并且诠释了有花植物如何通过受精诱导的花粉管吸引子降解来迅速阻断成功受精后的其它花粉管生长的分子机制。