受精依赖的卵细胞调控防止多精入卵的分子机制  

Fertilization-Dependent Mechanism of Egg Cell Preventing Polytubey

作　　者：禹小波 孙蒙祥[2] YU Xiaobo;SUN Mengxiang(Ministry of Education College of Bioengineering,Chongqing University,Chongqing 400044,China;College of Life Sciences,Wuhan University,Wuhan 430072,China)

机构地区：[1]重庆大学生物工程学院,重庆400044 [2]武汉大学生命科学学院,武汉430072

出　　处：《中国细胞生物学学报》2021年第7期1325-1330,共6页Chinese Journal of Cell Biology

基　　金：国家自然科学基金重大项目(批准号:31991201)资助的课题。

摘　　要：在动物受精过程中,卵母细胞皮层颗粒所分泌的蛋白酶在防止多精入卵中起着重要作用。在有花植物的有性生殖过程中,受精过程则更为复杂。这一过程涉及到花粉管所运输的一对不可移动的精子分别与卵细胞和中央细胞融合的过程。在通常情况下,每个胚珠只会吸引一根花粉管,从而有效地降低多精入卵可能性。植物受精后防止多余花粉管进入胚囊的机制长期以来一直不清楚。武汉大学植物生殖研究团队最近的一项工作发现卵细胞本身在防止多花粉进入胚囊的过程中发挥了重要的作用。卵细胞特异性地表达两个天冬氨酸蛋白酶基因ECS1和ECS2,其mRNA在成功受精之后会快速降解。ECS蛋白在卵细胞的顶端区域以类似于动物皮层颗粒网络的形式分布,且其分泌过程也是受精依赖的。ecs1ecs2双突变体的胚珠呈现吸引多花粉的表型。ECS1和ECS2能够特异性地切割花粉管吸引物质LURE1。ECS1和ECS2在助细胞中的异位表达则会导致LURE1蛋白水平的降低及花粉管吸引能力的减弱。因此,ECS1和ECS2快速防止了多余花粉管进入胚囊。上述发现揭示植物的卵细胞能够感知受精并建立起一种受精依赖的快速防止多花粉管进入胚囊的机制。In the process of fertilization in animals,proteases secreted from cortical granules of egg cells function to prevent polyspermy.In flowering plants,fertilization is more complex and involves a pair of non-motile sperm cells deliveres by a pollen tube,and then two sperm fuses with an egg cell and a central cell respectively.Usually,each ovule only attracts one pollen tube and thus efficiently reduces the possibility of polyspermy.However,the mechanism of plant preventing polytubey has remained unknown foe decades.Recently,it reports that the egg cell itself plays a critical role in preventing polytubey.Two aspartic proteases,ECS1 and ECS2,are specifically expressed in the egg cell and degraded soon after successful sperm-egg fusion.ECS locates at the apical domain of the Arabidopsis egg cell in the form of a cortical network.The secretion of ECS is triggered by sperm-egg fusion.The ecs1ecs2 double mutants showed polytubey phenotype.Further study reveales that ECS1 and ESC2 can cleave pollen tube attractant LURE1 specifically and thus quickly block the pollen tube attraction to prevent polytubey.These results indicate that plant egg cell can sense successful fertilization and establish a fertilization dependent mechanism to prevent polytubey.

关 键 词：卵细胞 花粉管 多精入卵 LURE1 天冬氨酸蛋白酶 受精 拟南芥 

分 类 号：Q945.6[生物学—植物学]