ABSTRACT

Onion bulb initiation is photoperiod-dependent. Understanding this is crucial for adapting new varieties for growth at different latitudes, as well as aiding germplasm screening for the choice of current varieties. This study aims to gain further understanding of the molecular mechanisms involved in onion bulbing process based on the parallels with well-characterised functional clock genes in the Arabidopsis flowering pathway. A comprehensive set of diurnal quantitative expression experiments was carried out to investigate the bulbing response in two different onion varieties, namely Renate, a long-day variety and Hojem, a short-day variety under increasing intermediate day-lengths. All onion homologous to Arabidopsis flowering time genes showed clear diurnal expression patterns peaking at different times of the day for both long/short-day onions, indicating their role in daylength dependent bulbing process at molecular level. Under intermediate daylengths, AcFT1 expression level increased with daylengths in both varieties, while AcFT4 was expressed in all daylengths. The two genes showed complementary expression with AcFT4 peaking in the morning and AcFT1 in the evening in longer days. The results indicate that AcFT1 and AcFT4 are negatively co-regulated, but AcFT1 is the predominant regulator of bulb formation in response to daylength.

摘要

洋葱球茎的启动依赖于光周期。了解这一点对于使新品种适应不同纬度的生长以及帮助种质筛选以选择当前品种至关重要。本研究旨在基于与拟南芥开花途径中充分表征的功能时钟基因的相似性，进一步了解参与洋葱球茎过程的分子机制。进行了一套全面的昼夜定量表达实验，以研究两种不同的洋葱品种，即长日照品种 Renate 和短日照品种 Hojem 在增加中间日照长度下的球茎反应。所有与拟南芥开花时间基因同源的洋葱都显示出明显的昼夜表达模式，对于长/短日洋葱来说，在一天的不同时间达到峰值，表明它们在分子水平上的日长依赖性膨胀过程中的作用。在中等白天长度下，AcFT1表达水平在两个品种中都随着日长而增加，而AcFT4在所有日长中都有表达。这两个基因显示出互补表达，AcFT4在早晨达到峰值，而AcFT1在更长的日子里在晚上达到峰值。结果表明AcFT1和 AcFT4 是负共调的，但 AcFT1 是响应日长的球茎形成的主要调节剂。