Beijing Key Laboratory of Development and Quality Control of Ornamental Crops, Department of Ornamental Horticulture, College of Horticulture, China Agricultural University, Beijing, 100193, China.
Robert W. Holley Center for Agriculture and Health, United States Department of Agriculture, Agricultural Research Service, Ithaca, 14853, NY, USA.
Plant J. 2019 Sep;99(6):1159-1171. doi: 10.1111/tpj.14412. Epub 2019 Jun 26.
The timing of plant organ abscission is modulated by the balance of two hormones, ethylene and auxin, while the mechanism of organ shedding depends on the loss of middle lamella pectin in the abscission zone (AZ). However, the mechanisms involved in sensing the balance of auxin and ethylene and that affect pectin degradation during abscission are not well understood. In this study, we identified two members of the APETALA2/ethylene-responsive factor (AP2/ERF) transcription factor family in rose (Rosa hybrida), RhERF1 and RhERF4 which play a role in petal abscission. The expression of RhERF1 and RhERF4 was influenced by ethylene and auxin, respectively. Reduced expression of RhERF1 or RhERF4 was observed to accelerate petal abscission. Global expression analysis and real-time PCR assays revealed that RhERF1 and RhERF4 modulate the expression of genes encoding pectin-metabolizing enzymes. A reduction in the abundance of pectin epitopes was detected in the AZs of RhERF1 and RhERF4-silenced plants by immunofluorescence microscopy analysis. In addition, RhERF1 and RhERF4 were shown to bind to the promoter of the pectin-metabolizing gene β-GALACTOSIDASE 1 (RhBGLA1), and reduced expression of RhBGLA1 delayed petal abscission. We conclude that during petal abscission, RhERF1 and RhERF4 integrate and coordinate ethylene and auxin signals to modulate pectin metabolism, in part by regulating the expression of RhBGLA1.
植物器官脱落的时间由乙烯和生长素两种激素的平衡来调节，而器官脱落的机制则取决于脱落区（AZ）中层果胶的丧失。然而，对于感受生长素和乙烯平衡以及影响脱落过程中果胶降解的机制还了解甚少。在这项研究中，我们在玫瑰（Rosa hybrida）中鉴定了 APETALA2/ethylene-responsive factor (AP2/ERF) 转录因子家族的两个成员，RhERF1 和 RhERF4，它们在花瓣脱落中起作用。RhERF1 和 RhERF4 的表达分别受乙烯和生长素的影响。观察到 RhERF1 或 RhERF4 的表达减少会加速花瓣脱落。全局表达分析和实时 PCR 分析表明，RhERF1 和 RhERF4 调节编码果胶代谢酶的基因的表达。通过免疫荧光显微镜分析检测到 RhERF1 和 RhERF4 沉默植物的 AZ 中果胶表位的丰度降低。此外，还表明 RhERF1 和 RhERF4 与果胶代谢基因β-GALACTOSIDASE 1（RhBGLA1）的启动子结合，并且 RhBGLA1 的表达减少会延迟花瓣脱落。我们的结论是，在花瓣脱落过程中，RhERF1 和 RhERF4 整合并协调乙烯和生长素信号以调节果胶代谢，部分是通过调节 RhBGLA1 的表达来实现的。
