Abstract
Key messageGmFULa improved soybean yield by enhancing carbon assimilation. Meanwhile, different from known yield-related genes, it did not alter flowering time or maturity.Soybean (Glycine max (L.) Merr.) is highly demanded by a continuously growing human population. However, increasing soybean yield is a major challenge. FRUITFULL (FUL), a MADS-box transcription factor, plays important roles in multiple developmental processes, especially fruit and pod development, which are crucial for soybean yield formation. However, the functions of its homologs in soybean are not clear. Here, through haplotype analysis, we found that one haplotype of the soybean homolog GmFULa (GmFULa-H02) is dominant in cultivated soybeans, suggesting that GmFULa-H02 was highly selected during domestication and varietal improvement of soybean. Interestingly, transgenic overexpression of GmFULa enhanced vegetative growth with more biomass accumulated and ultimately increased the yield but without affecting the plant height or changing the flowering time and maturity, indicating that it enhances the efficiency of dry matter accumulation. It also promoted the yield factors like branch number, pod number and 100-seed weight, which ultimately increased the yield. It increased the palisade tissue cell number and the chlorophyll content to promote photosynthesis and increase the soluble sugar content in leaves and fresh seeds. Furthermore, GmFULa were found to be sublocalized in the nucleus and positively regulate sucrose synthases (SUSs) and sucrose transporters (SUTs) by binding with the conserved CArG boxes in their promoters. Overall, these results showed GmFULa promotes the capacity of assimilation and the transport of the resultant assimilates to increase yield, and provided insights into the link between GmFULa and sucrose synthesis with transport-related molecular pathways that control seed yield.
Highlights
Soybean (Glycine max (L.) Merr.) provides large amounts of edible oils and vegetable proteins for humans and livestock, and demand for soybean is increasing globally due to human population growth
Our results show that the GmFULa–GmSUSs/GmSUTs pathway regulates the seed yield of soybean, controls the cell number of palisade tissue, and enhances organic matter accumulation by increasing whole-soluble sugar contents in leaf tissue
Combined with the observation that GmFULa was highly expressed in the shoot apices (Jia et al 2015), which strongly indicates that GmFULa should have an important role in yield
Summary
Soybean (Glycine max (L.) Merr.) provides large amounts of edible oils and vegetable proteins for humans and livestock, and demand for soybean is increasing globally due to human population growth. Soybean yield is based on pod number per plant, seed number per pod and 100-seed weight (Van Roekel et al 2015; Yan et al 2017; Bianchi et al 2020). GmCYP78A10 is related to pod number and 100-seed weight and Ln is a major gene controlling fourseed pod development in soybean (Jeong et al 2012; Wang et al 2015; Sayama et al 2017). GsCID1 is responsible for 100-seed weight in wild soybean (Hu et al 2020). GmKIX8-1 was demonstrated to be associated with soybean seed weight (Nguyen et al 2021). The molecular mechanism controlling yield in soybean is largely unknown
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