Abstract
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.
Highlights
The photoperiod is demarcated as the portion of light and dark hours in a diurnal cycle of 24 h [1]
The expression of GI, FKF1, and ZTL homologs under short-day and long-day environments was observed using quantitative reverse transcription-PCR, where the results presented that key genes—namely GI, CO, and FLOWERING LOCUS T (FT)—controlling photoperiodic flowering in Arabidopsis are conserved in Alliums, and a role for these genes in the photoperiodic control of bulb instigation is anticipated [12,13]
The expression of GI, FKF1, and ZTL homologs under short-day and long-day environments was observed using quantitative reverse transcription-PCR, where the results presented that key genes—namely GI, CO, and FT—controlling photoperiodic flowering in Arabidopsis are conserved in onion, and a role fIontr. tJ.hMesole
Summary
The photoperiod is demarcated as the portion of light and dark hours in a diurnal cycle of 24 h [1]. Further research in onion exhibited that diverse FT genes control bulb enlargement, stressing the evolutionary-focused maintenance of FT proteins as key producers of the bulb alteration This too influences the offshoot meristems at the axillary buds and vascular cambium etches for this progressive changeover. This research work displays that the ectopic expression of TLOG1, which is a cytokinin-activating gene, gives axillary tomato meristems the capability to produce midair tiny tubers that reflect the involvement of cytokinin in initiating the storage organ development in a non-tuberizing plant. Throughout evolution, a quantity of plant classes has achieved the skill of distinguishing their leaves, stems, or roots into storage organs (bulb), as observed in garlic and onion The formation of these bulbs is attracted throughout drought and freezing conditions that pacify plant feasibility, acting as a mechanism for asexual propagation that delivers a survival strategy to the plant. Understanding the mechanisms recycled by the plant to signal the distinction of these bulbs is a vital area to see the nutritious stresses of the increasing world population, and it is an ultimate query in developing environmental skills
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