Innovation of a Regulatory Mechanism Modulating Semi-determinate Stem Growth through Artificial Selection in Soybean

Abstract

It has been demonstrated that Terminal Flowering 1 (TFL1) in Arabidopsis and its functional orthologs in other plants specify indeterminate stem growth through their specific expression that represses floral identity genes in shoot apical meristems (SAMs), and that the loss-of-function mutations at these functional counterparts result in the transition of SAMs from the vegetative to reproductive state that is essential for initiation of terminal flowering and thus formation of determinate stems. However, little is known regarding how semi-determinate stems, which produce terminal racemes similar to those observed in determinate plants, are specified in any flowering plants. Here we show that semi-determinacy in soybean is modulated by transcriptional repression of Dt1, the functional ortholog of TFL1, in SAMs. Such repression is fulfilled by recently enabled spatiotemporal expression of Dt2, an ancestral form of the APETALA1/FRUITFULL orthologs, which encodes a MADS-box factor directly binding to the regulatory sequence of Dt1. In addition, Dt2 triggers co-expression of the putative SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (GmSOC1) in SAMs, where GmSOC1 interacts with Dt2, and also directly binds to the Dt1 regulatory sequence. Heterologous expression of Dt2 and Dt1 in determinate (tfl1) Arabidopsis mutants enables creation of semi-determinacy, but the same forms of the two genes in the tfl1 and soc1 background produce indeterminate stems, suggesting that Dt2 and SOC1 both are essential for transcriptional repression of Dt1. Nevertheless, the expression of Dt2 is unable to repress TFL1 in Arabidopsis, further demonstrating the evolutionary novelty of the regulatory mechanism underlying stem growth in soybean.

Genome-Wide Identification and Characterization of MADS-box Family Genes Related to Floral Organ Development and Stress Resistance in Hevea brasiliensis Müll. Arg.

“…These results revealed that most of the HbMADS-box genes (69.2% belong to the first, second, and third groups) within the same group shared conserved exon-intron structures, and the other HbMADS-box genes (30.8% of the fourth to eighth groups) with the different exon-intron structures may belong to distinct types of HbMADS-box genes in the rubber tree (Table S5). These characteristics are consistent with the features of MADS-box genes in other flowering plants, such as Arabidopsis, Oryza sativa, and Vitis vinifera [45][46][47].…”

Genome-wide association studies dissect the genetic networks underlying agronomical traits in soybean

“…Epistasis, or the interaction between genes, plays an important role in controlling complex inheritance [ 34 ]. For instance, Dt1 exerts an epistatic effect on Dt2 in the regulation of plant height in soybean [ 35 , 36 ]. In this study, we detected three SAL for plant height using all tested accessions (Fig.…”

Exploring the QTL–allele constitution of main stem node number and its differentiation among maturity groups in a Northeast China soybean population

“…In the literature, the soybean stem growth habit genes ( Dt1 and Dt2 ) and E genes conferring flowering and maturity were considered to be related to MSN (Chang, et al., 2018; Fang, et al., 2017), but the Dt1 gene was not identified in our study. That might be because the breeding priority in NEC tended to be semi‐determinant stem termination conferred by a dominant allele Dt2 in the genetic background of Dt1 (Bernard, 1972; Liu et al., 2016; Xue, Wei, Tang, & Liu, 2015). The present candidate MSN gene results as a gene system are to be further validated, which may take great future effort.…”