Abstract
Soybean is an important crop that is grown worldwide. Flowering time is a critical agricultural trait determining successful reproduction and yields. For plants, light and temperature are important environmental factors that regulate flowering time. Soybean is a typical short-day (SD) plant, and many studies have elucidated the fine-scale mechanisms of how soybean responds to photoperiod. Low temperature can delay the flowering time of soybean, but little is known about the detailed mechanism of how temperature affects soybean flowering. In this study, we isolated GmFLC-like from soybean, which belongs to the FLOWERING LOCUS C clade of the MADS-box family and is intensely expressed in soybean leaves. Heterologous expression of GmFLC-like results in a delayed-flowering phenotype in Arabidopsis. Additional experiments revealed that GmFLC-like is involved in long-term low temperature-triggered late flowering by inhibiting FT gene expression. In addition, yeast one-hybrid, dual-luciferase reporter assay, and electrophoretic mobility shift assay revealed that the GmFLC-like protein could directly repress the expression of FT2a by physically interacting with its promoter region. Taken together, our results revealed that GmFLC-like functions as a floral repressor involved in flowering time during treatments with various low temperature durations. As the only the FLC gene in soybean, GmFLC-like was meaningfully retained in the soybean genome over the course of evolution, and this gene may play an important role in delaying flowering time and providing protective mechanisms against sporadic and extremely low temperatures.
Highlights
Understanding the molecular mechanism driving the change from vegetative to reproductive growth is crucial for maximizing the yield of seed crops in a given environment
We found that overexpression of AtDREB1A in soybean caused clearly delayed flowering [44]. qRT-PCR analyses of the expression of flowering time genes related to the vernalization pathway showed that Glyma11g13220 (GmVRN1-like) and Glyma05g28130 were strongly upregulated in the DEHYDRATION RESPONSE ELEMENT B1A (AtDREB1A)-overexpressing soybean [45]
To identify the functions of Glyma05g28130 in regulating flowering time, we cloned the gene from the soybean cultivar “Huachun 5” referring to the sequence found in the Phytozome database [47]
Summary
Understanding the molecular mechanism driving the change from vegetative to reproductive growth is crucial for maximizing the yield of seed crops in a given environment. As one of the most important traits, flowering is considered the developmental transition from juvenile to adult phase, and the flowering process is regulated by various internal signals and environmental cues. Light, including the duration, quality, and intensity, is one of the most important environmental cues modulating flowering at multiple levels [5]. The change in light quality triggers multiple responses referred to as the “shade avoidance syndrome”. One of most important parameters for light, has independent functions in the regulation of flowering time by accelerating the transition from juvenile to adult phase in Arabidopsis and other higher plants [5]
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