Ln Is a Key Regulator of Leaflet Shape and Number of Seeds per Pod in Soybean

Narrow leaflet soybean ( Glycine max ) varieties tend to have more seeds per pod than broad leaflet varieties. Narrow leaflet in soybean is conferred by a single recessive gene, ln . Here, we show that the transition from broad ( Ln ) to narrow leaflet ( ln ) is associated with an amino acid substitution in the EAR motif encoded by a gene (designated Gm- JAGGED1 ) homologous to Arabidopsis JAGGED ( JAG ) that regulates lateral organ development and the variant exerts a pleiotropic effect on fruit patterning. The genomic region that regulates both the traits was mapped to a 12.6-kb region containing only one gene, Gm- JAG1 . Introducing the Gm- JAG1 allele into a loss-of-function Arabidopsis jagged mutant partially restored the wild-type JAG phenotypes, including leaf shape, flower opening, and fruit shape, but the Gm- jag1 ( ln ) and EAR-deleted Gm- JAG1 alleles in the jagged mutant did not result in an apparent phenotypic change. These observations indicate that despite some degree of functional change of Gm- JAG1 due to the divergence from Arabidopsis JAG , Gm- JAG1 complemented the functions of JAG in Arabidopsis thaliana . However, the Gm- JAG1 homoeolog, Gm- JAG2 , appears to be sub- or neofunctionalized, as revealed by the differential expression of the two genes in multiple plant tissues, a complementation test, and an allelic analysis at both loci.