Alamar M Carmen, Anastasiadi Maria, Lopez-Cobollo Rosa, Bennett Mark H, Thompson Andrew J, Turnbull Colin G N, Mohareb Fady, Terry Leon A
Cranfield University, Bedfordshire, MK43 0AL, UK.
Department of Life Sciences, Imperial College London, London, SW7 2AZ, UK.
Postharvest Biol Technol. 2020 Oct;168:111267. doi: 10.1016/j.postharvbio.2020.111267.
Control of dormancy and sprouting in onion bulbs is commercially important for postharvest management. Although ethylene application is sometimes used to extend dormancy, the underlying mechanisms regulating dormancy transition remain unclear. Since the sprout leaves emerge from the bulb baseplate, we used this tissue to assess the impact of ethylene treatment and storage time on the hormone profile and the transcriptome. Reads from 30 libraries were assembled and annotated, with 94,840 unigenes retained after filtering. The transcriptome assembly was of high quality and continuity (N50: 1809 bp, GC content: 36.21 %), and was used to analyse differential expression and Gene Onotologies. Across two years, applied ethylene resulted in delayed dormancy break and reduced post-dormancy sprout vigour. Ethylene supplementation enhanced endogenous ethylene production and caused a transient climacteric-like increase in respiration. Significant changes in hormone and associated transcript profiles occurred through storage and in response to ethylene. In particular, abscisic acid (ABA) and its metabolite phaseic acid (PA) increased under ethylene during the longer dormancy period; however, cytokinin increases observed during storage appeared largely independent of ethylene treatment. Several hormone-related transcripts showed differential expression over time and/or in response to ethylene. Expression of ethylene biosynthesis (), receptor () and transcription factor () genes were modified by ethylene, as were ABA biosynthesis genes such and cytokinin biosynthesis genes such as and . We conclude that ethylene substantially modifies expression of genes in several phytohormone pathways, and some of these changes may underlie the dormancy-extending effects of exogenous ethylene.
控制洋葱鳞茎的休眠和发芽对采后管理具有重要的商业意义。尽管有时会使用乙烯处理来延长休眠期，但调节休眠转变的潜在机制仍不清楚。由于发芽的叶子从鳞茎底盘长出，我们利用该组织评估乙烯处理和储存时间对激素谱和转录组的影响。对来自30个文库的读数进行了组装和注释，过滤后保留了94,840个单基因。转录组组装具有高质量和连续性（N50：1809 bp，GC含量：36.21%），并用于分析差异表达和基因本体。在两年的时间里，施用乙烯导致休眠打破延迟，休眠后发芽活力降低。补充乙烯增强了内源性乙烯的产生，并导致呼吸作用出现类似跃变的短暂增加。在储存过程中以及对乙烯的反应中，激素和相关转录谱发生了显著变化。特别是，在较长的休眠期内，脱落酸（ABA）及其代谢产物阶段酸（PA）在乙烯作用下增加；然而，在储存期间观察到的细胞分裂素增加似乎在很大程度上与乙烯处理无关。一些与激素相关的转录本在不同时间和/或对乙烯的反应中表现出差异表达。乙烯生物合成（）、受体（）和转录因子（）基因的表达受到乙烯的修饰，ABA生物合成基因如和细胞分裂素生物合成基因如和也是如此。我们得出结论，乙烯显著改变了几种植物激素途径中基因的表达，其中一些变化可能是外源乙烯延长休眠作用的基础。
