Abstract
Photoperiod is one of the main climatic factors that determine flowering time and yield. Some members of the INDETERMINATE DOMAIN (IDD) transcription factor family have been reported to be involved in regulation of flowering time in Arabidopsis, maize, and rice. In this study, the domain analysis showed that GmIDD had a typical ID domain and was a member of the soybean IDD transcription factor family. Quantitative real-time PCR analysis showed that GmIDD was induced by short day conditions in leaves and regulated by circadian clock. Under long day conditions, transgenic Arabidopsis overexpressing GmIDD flowered earlier than wild-type, and idd mutants flowered later, while the overexpression of GmIDD rescued the late-flowering phenotype of idd mutants. Chromatin immunoprecipitation sequencing assays of GmIDD binding sites in GmIDD-overexpression (GmIDD-ox) Arabidopsis further identified potential direct targets, including a transcription factor, AGAMOUS-like 18 (AGL18). GmIDD might inhibit the transcriptional activity of flower repressor AGL18 by binding to the TTTTGGTCC motif of AGL18 promoter. Furthermore, the results also showed that GmIDD overexpression increased the transcription levels of flowering time-related genes FLOWERING LOCUS T (FT), SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1), LEAFY (LFY) and APETALA1 (AP1) in Arabidopsis. Taken together, GmIDD appeared to inhibit the transcriptional activity of AGL18 and induced the expression of FT gene to promote Arabidopsis flowering.
Highlights
Soybean [Glycine max (L.) Merrill] is a typical short-day (SD) plant, which is sensitive to photoperiod response
We have identified that both genes such as GmRAV and GmGBP1 induced by SD detected by suppression subtractive hybridization (SSH) functioned in regulating flowering time (Zhao et al, 2008, 2018)
The domain analysis showed that GmIDD had a typical ID domain, which consisted of a nuclear localization signal motif (KKKR), four zinc finger domains including two types of C2H2 (72–92 aa and 114–142 aa), and two types of C2HC (149–169 aa and 176–195 aa) (Figure 1A)
Summary
Soybean [Glycine max (L.) Merrill] is a typical short-day (SD) plant, which is sensitive to photoperiod response. Flowering time and mature period have become important agronomic traits of soybean, which can influence the yield, quality, and versatility of soybean varieties. By reasonable planting of soybean varieties under different environmental conditions in different regions, the cultivated land resources in this area can be fully utilized, which is of great significance to increase the yield of soybean. It is a hotspot in the field of reducing the breeding pressure, by exploring new photoperiod genes that control soybean flowering and maturation, and further clarifying the molecular mechanism of these genes involved in soybean photoperiod effect
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