Department of Vegetable Science, College of Horticulture, Northwest A&F University, Yangling 712100, China.
Vegetable Crops Program, National Agricultural Research Centre, Islamabad 44000, Pakistan.
Int J Mol Sci. 2020 Feb 16;21(4):1325. doi: 10.3390/ijms21041325.
The photoperiod marks a varied set of behaviors in plants, including bulbing. Bulbing is controlled by inner signals, which can be stimulated or subdued by the ecological environment. It had been broadly stated that phytohormones control the plant development, and they are considered to play a significant part in the bulb formation. The past decade has witnessed significant progress in understanding and advancement about the photoperiodic initiation of bulbing in plants. A noticeable query is to what degree the mechanisms discovered in bulb crops are also shared by other species and what other qualities are also dependent on photoperiod. The FLOWERING LOCUS T (FT) protein has a role in flowering; however, the FT genes were afterward reported to play further functions in other biological developments (e.g., bulbing). This is predominantly applicable in photoperiodic regulation, where the FT genes seem to have experienced significant development at the practical level and play a novel part in the switch of bulb formation in Alliums. The neofunctionalization of FT homologs in the photoperiodic environments detects these proteins as a new class of primary signaling mechanisms that control the growth and organogenesis in these agronomic-related species. In the present review, we report the underlying mechanisms regulating the photoperiodic-mediated bulb enlargement in Allium species. Therefore, the present review aims to systematically review the published literature on the bulbing mechanism of Allium crops in response to photoperiod. We also provide evidence showing that the bulbing transitions are controlled by phytohormones signaling and FT-like paralogues that respond to independent environmental cues (photoperiod), and we also show that an autorelay mechanism involving FT modulates the expression of the bulbing-control gene. Although a large number of studies have been conducted, several limitations and research gaps have been identified that need to be addressed in future studies.
光周期标志着植物的一系列不同行为，包括鳞茎形成。鳞茎形成受内在信号控制，这些信号可以被生态环境刺激或抑制。人们曾广泛认为植物激素控制着植物的发育，并且它们在鳞茎形成中起着重要作用。过去十年，人们对植物光周期诱导鳞茎形成的机制有了更深入的理解和认识。一个引人关注的问题是，在鳞茎作物中发现的机制在多大程度上也存在于其他物种中，以及还有哪些特性也依赖于光周期。FT 蛋白在开花中起作用；然而，后来报道称，FT 基因在其他生物发育过程中（例如鳞茎形成）发挥了进一步的作用。这在光周期调控中尤为明显，FT 基因在实际水平上似乎经历了显著的发展，并在 Alliums 鳞茎形成的开关中扮演了新的角色。在光周期环境中，FT 同源物的新功能化检测到这些蛋白质作为一类新的初级信号机制，控制着这些与农业相关物种的生长和器官发生。在本综述中，我们报告了调节 Allium 物种光周期介导的鳞茎增大的潜在机制。因此，本综述旨在系统地综述关于 Allium 作物对光周期响应的鳞茎形成机制的已发表文献。我们还提供了证据表明，鳞茎转化受植物激素信号和 FT 样同源物控制，这些同源物对独立的环境信号（光周期）做出反应，我们还表明，涉及 FT 的自动反馈机制调节了鳞茎控制基因的表达。尽管已经进行了大量的研究，但仍发现了一些局限性和研究空白，需要在未来的研究中解决。
