Soybean (Glycine max) is highly sensitive to photoperiod, which affects flowering time and plant architecture and thus limits the distribution range of elite soybean cultivars. The major maturity gene E1 confers the most prominent effect on photoperiod sensitivity, but its downstream signaling pathway remains largely unknown. Here, we confirm that the encoded E1 protein is a transcriptional repressor. The expression of seven GmMDE genes (Glycine max MADS-box genes downregulated by E1) was suppressed when E1 was overexpressed and promoted when E1 was knocked out through CRISPR/Cas9-mediated mutagenesis. These GmMDEs exhibited similar tissue specificity and expression patterns, including in response to photoperiod, E1 expression, and E1 genotype. E1 repressed GmMDE promoter activity. Results for two GmMDEs showed that E1 epigenetically silences their expression by directly binding to their promoters to increase H3K27me3 levels. Overexpression of GmMDE06 promoted flowering and post-flowering termination of stem growth. The late flowering phenotype of E1-overexpressing soybean lines was reversed by overexpression of GmMDE06, placing GmMDE06 downstream of E1. Overexpression of GmMDE06 increased the expression of the soybean FLOWERING LOCUS T orthologs GmFT2a and GmFT5a, leading to feedback upregulation of GmMDE, indicating that GmMDE and GmFT2a/GmFT5a form a positive regulatory feedback loop promoting flowering. GmMDE06 also promoted post-flowering termination of stem growth by repressing the expression of the shoot identity gene Dt1. The E1-GmMDEs-GmFT2a/5a-Dt1 signaling pathway illustrates how soybean responds to photoperiod by modulating flowering time and post-flowering stem termination.

No abstract

No abstract

Soybean (Glycine max (Linn.) Merr.) is a widely-cultivated crop, the yield of which is markedly affected by adverse environmental conditions. Soil salinization, in particular, has led to the degradation of agricultural land, resulting in poor plant growth and decreased crop yields. In plants, serine/threonine protein kinases (STKs) are involved in the plant response to a variety of abiotic stresses. Our previous study identified a transcription factor (GmWRKY20) involved in plant stress resistance, which can directly regulate the expression of GmSTK12. Here, we investigated the effect of the stress-responsive gene GmSTK12 (Glyma.12g198200), which encodes a serine/threonine protein kinase, on soybean salt tolerance. Overall, the overexpression of GmSTK12 (GmSTK12-OE) resulted in increased salt tolerance. Under salt stress, GmSTK12-OE soybeans exhibited significantly increased chlorophyll and proline (PRO) contents; decreased relative electrical conductivity; decreased malondialdehyde (MDA) and superoxide anion (O2−) contents; and increased activities of the antioxidant enzymes catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD). The nitroblue tetrazolium chloride (NBT) staining experiment further confirmed the reduced accumulation of reactive oxygen species (ROS) in GmSTK12-OE soybean leaves. We further determined the Na+ and K+ contents in soybean leaves and roots and found that the Na+ content and Na+/K+ ratio in GmSTK12-OE soybean leaves and roots were significantly lower than those of WT (williams82) soybeans. Furthermore, quantitative real-time PCR (qRT-PCR) analysis revealed that the expression of three SOS pathway genes (GmSOS1, GmSOS2a, and GmSOS2b) was upregulated in GmSTK12-OE soybeans under salt stress. Taken together, the results indicate that GmSTK12 is involved in the mechanism of soybean response to salt stress.

Copper Chaperone For Superoxide Dismutase (CCS) genes encode copper chaperone for Superoxide dismutase (SOD) and dramatically affect the activity of SOD through regulating copper delivery from target to SOD. SOD is the effective component of the antioxidant defense system in plant cells to reduce oxidative damage by eliminating Reactive oxygen species (ROS), which are produced during abiotic stress. CCS might play an important role in abiotic stress to eliminate the damage caused by ROS, however, little is known about CCS in soybean in abiotic stress regulation. In this study, 31 GmCCS gene family members were identified from soybean genome. These genes were classified into 4 subfamilies in the phylogenetic tree. Characteristics of 31 GmCCS genes including gene structure, chromosomal location, collinearity, conserved domain, protein motif, cis-elements, and tissue expression profiling were systematically analyzed. RT-qPCR was used to analyze the expression of 31 GmCCS under abiotic stress, and the results showed that 5 GmCCS genes(GmCCS5, GmCCS7, GmCCS8, GmCCS11 and GmCCS24) were significantly induced by some kind of abiotic stress. The functions of these GmCCS genes in abiotic stress were tested using yeast expression system and soybean hairy roots. The results showed that GmCCS7/GmCCS24 participated in drought stress regulation. Soybean hairy roots expressing GmCCS7/GmCCS24 showed improved drought stress tolerance, with increased SOD and other antioxidant enzyme activities. The results of this study provide reference value in-depth study CCS gene family, and important gene resources for the genetic improvement of soybean drought stress tolerance.