Abstract
The soybean (Glycine max (L.) Merr.) is an important oil and food crop. Its growth and development is regulated by complex genetic networks, and there are still many genes with unknown functions in regulation pathways. In this study, GmNMHC5, a member of the MADS-box protein family, was found to promote flowering and maturity in the soybean. Gene expression profiling in transgenic plants confirmed that the 35S:GmNMHC5 T3 generation had early flowering and precocity. We used CRISPR-Cas9 to edit GmNMHC5 and found that late flowering and maturity occurred in Gmnmhc5 lines with stable inheritance. Remarkably, in the 35S:GmNMHC5 plants, the expression of flowering inhibitors GmFT1a and GmFT4 was inhibited. In addition, overexpression of GmNMHC5 in ft-10 (a late flowering Arabidopsis thaliana mutant lacking Flowering Locus T (FT) function) rescued the extremely late-flowering phenotype of the mutant A. thaliana. These results suggest that GmNMHC5 is a positive transcription factor of flowering and maturity in the soybean, which has a close relationship with FT homologs in the flowering regulation pathway. This discovery provides new ideas for the improvement of the flowering regulation network, and can also provide guidance for future breeding work.
Highlights
The MADS-box family is an important transcriptional regulator in plants
We propose that GmNMHC5 is a positive regulator of flowering, and the soybean has developed a balanced pathway to control flowering through coordinated regulation between the flowering promoter GmNMHC5 and repressors GmFT1a and GmFT4
We found that GmNMHC5 overexpression in homozygous lines promoted flowering
Summary
The MADS-box family is an important transcriptional regulator in plants. Members of this family have a similar secondary structure including the N-terminal DNA-binding MADS-box domain. The MADS-box domain is followed by an intervening region, the K-box, involved in protein–protein interactions, and the C-terminus, in which the divergence among members is greater [1]. MADS-box family proteins play a wide range of functions in plants, especially in the regulation of flowering time and the development of various reproductive organs [2,3,4]. The Arabidopsis MADS-box genes, e.g., AGAMOUS-LIKE 20 (AGL20), SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1. (SOC1), and AGAMOUS-LIKE 28 (AGL28), positively regulate the flowering process [5,6,7]. AGAMOUS-LIKE 18 (AGL18) negatively regulates flowering [8]
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