Abstract
Yield enhancement is a top priority for soybean (Glycine max Merr.) breeding. SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) is a major integrator in flowering pathway, and it is anticipated to be capable of regulating soybean reproductive stages through its interactions with other MADS-box genes. Thus, we produced transgenic soybean for a constitutive expression of a maize SOC1 (ZmSOC1). T1 transgenic plants, in comparison with the nontransgenic plants, showed early flowering, reduced height of mature plants, and no significant impact on grain quality. The transgenic plants also had a 13.5–23.2% of higher grain weight per plant than the nontransgenic plants in two experiments. Transcriptome analysis in the leaves of 34-day old plants revealed 58 differentially expressed genes (DEGs) responding to the expression of the ZmSOC1, of which the upregulated FRUITFULL MADS-box gene, as well as the transcription factor VASCULAR PLANT ONE-ZINC FINGER1, contributed to the promoted flowering. The downregulated gibberellin receptor GID1B could play a major role in reducing the plant height. The remaining DEGs suggested broader effects on the other unmeasured traits (e.g., photosynthesis efficiency and abiotic tolerance), which could contribute to yield increase. Overall, modulating expression of SOC1 in soybean provides a novel and promising approach to regulate plant growth and reproductive development and thus has a potential either to enhance grain yield or to change plant adaptability.
Highlights
Yield enhancement is a top priority for soybean (Glycine max Merr.) breeding
The differentially expressed genes (DEGs) responding to the expression of the ZmSOC1 suggested broader effects of the ZmSOC1 on plant height, flowering time, and the other unmeasured traits, which could contribute to yield increase
Soybean is a photoperiod-sensitive crop. Both plant height and days to flowering and maturity are of importance for soybean adaptability and yield
Summary
Yield enhancement is a top priority for soybean (Glycine max Merr.) breeding. SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) is a major integrator in flowering pathway, and it is anticipated to be capable of regulating soybean reproductive stages through its interactions with other MADS-box genes. In the Approval Database of genetically modified (GM) crops, 41 GM soybean events are listed, including 11 events with a GM trait of modified oil/fatty acid, one event “Verdeca HB4 Soybean” containing a sunflower (Helianthus annuus) HAHB-4 gene for drought tolerance[13,14], and one event containing Arabidopsis thaliana B-BOX32 domain gene (BBX32) for enhanced photosynthesis/yield[15,16] (http://www.isaaa.org). In 2018, 123.5 million hectares soybeans were planted in the world, of which 95.9 million hectares (78%) were transgenics with either HT (69.3 million hectares) or HT/IR (26.6 million hectares), total accounting for 50% of the global area of biotech crops (http://www.isaaa.org). Neither of the HB4 soybean for abiotic tolerance nor the BBX32 soybean for enhanced photosynthesis/yield has been made available for commercialization (http://www.isaaa.org). Recent field tests suggested that the HB4 soybeans were able to increase seed yield in warm and dry environment by changing plant architecture and improving drought tolerance[14]
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