Chersicola Marko, Kladnik Aleš, Tušek Žnidarič Magda, Mrak Tanja, Gruden Kristina, Dermastia Marina
Department of Biotechnology and Systems Biology, National Institute of BiologyLjubljana, Slovenia.
Jožef Stefan International Postgraduate SchoolLjubljana, Slovenia.
Front Plant Sci. 2017 Mar 31;8:464. doi: 10.3389/fpls.2017.00464. eCollection 2017.
Ethylene has impact on several physiological plant processes, including abscission, during which plants shed both their vegetative and reproductive organs. Cell separation and programmed cell death are involved in abscission, and these have also been correlated with ethylene action. However, the detailed spatiotemporal pattern of the molecular events during abscission remains unknown. We examined the expression of two tomato genes, , and that encode the last enzyme in ethylene biosynthesis, 1-aminocyclopropane-1-carboxylate oxidase (ACO), together with the expression of other abscission-associated genes involved in cell separation and programmed cell death, during a period of 0-12 h after abscission induction in the tomato flower pedicel abscission zone and nearby tissues. In addition, we determined their localization in specific cell layers of the flower pedicel abscission zone and nearby tissues obtained by laser microdissection before and 8 h after abscission induction. The expression of both genes was localized to the vascular tissues in the pedicel. While was more uniformly expressed in all examined cell layers, the main expression site of was in cell layers just outside the abscission zone in its proximal and distal part. We showed that after abscission induction, ACO1 protein was synthesized in phloem companion cells, in which it was localized mainly in the cytoplasm. Samples were additionally treated with 1-methylcyclopropene (1-MCP), a competitive inhibitor of ethylene actions, and analyzed 8 h after abscission induction. Cell-layer-specific changes in gene expression were observed together with the specific localization and ethylene sensitivity of the hallmarks of cell separation and programmed cell death. While treatment with 1-MCP prevented separation of cells through inhibition of the expression of polygalacturonases, which are the key enzymes involved in degradation of the middle lamella, this had less impact on the occurrence of different kinds of membrane vesicles and abscission-related programmed cell death. In the flower pedicel abscission zone, the physical progressions of cell separation and programmed cell death are perpendicular to each other and start in the vascular tissues.
乙烯对植物的多种生理过程有影响，包括脱落，在此过程中植物会脱落其营养器官和生殖器官。细胞分离和程序性细胞死亡参与了脱落过程，并且这些过程也与乙烯的作用相关。然而，脱落过程中分子事件的详细时空模式仍然未知。我们研究了两个番茄基因，即编码乙烯生物合成最后一种酶1-氨基环丙烷-1-羧酸氧化酶（ACO）的基因，以及其他参与细胞分离和程序性细胞死亡的脱落相关基因在番茄花柄脱落区及附近组织脱落诱导后0至12小时内的表达情况。此外，我们确定了它们在脱落诱导前和诱导后8小时通过激光显微切割获得的花柄脱落区及附近组织特定细胞层中的定位。两个基因的表达都定位于花柄的维管组织。虽然在所有检测的细胞层中表达较为均匀，但主要在脱落区近端和远端外侧的细胞层中表达。我们发现，脱落诱导后，ACO1蛋白在韧皮部伴胞中合成，主要定位于细胞质中。样品还额外用乙烯作用的竞争性抑制剂1-甲基环丙烯（1-MCP）处理，并在脱落诱导后8小时进行分析。观察到基因表达的细胞层特异性变化以及细胞分离和程序性细胞死亡标志的特定定位和乙烯敏感性。虽然用1-MCP处理通过抑制多聚半乳糖醛酸酶的表达来阻止细胞分离，多聚半乳糖醛酸酶是参与中胶层降解的关键酶，但这对不同种类膜泡的出现和脱落相关的程序性细胞死亡影响较小。在花柄脱落区，细胞分离和程序性细胞死亡的物理进程相互垂直，并始于维管组织。
