Submitted to: Proceedings of the National Academy of Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/2/2010
Publication Date: 5/11/2010
Publication URL: http://hdl.handle.net/10113/41718
Citation: Tian, Z., Wang, X., Lee, R., Li, Y., Specht, J.E., Nelson, R.L., McClean, P.E., Qiu, I., Ma, J. 2010. Artificial Selection for Determinate Growth Habit in Soybean. In: Proceedings of the National Academy of Sciences. PNAS 107(19):8563-8568. Available: www.pnas.org/cgi/doi/10.1073/pnas.1000088107. Interpretive Summary: Much is known about the genetic variability of soybean germplasm for traits that can be visually observed or seed composition traits that can be physically measured. Very little is know about the specific genes that produce these variations and even less is know about the variation that exists within those genes. The gene that controls stem termination in soybean has a very large and obvious effect, and is also very economically important in U.S. soybean production. In this research, we identified the specific gene that controls stem termination, determined the range of variation for that gene in a diverse set of soybean and wild soybean germplasm, and were able to associate single amino acid changes with visual differences in plant structure. These genetic changes are part of the domestication process because none of the mutations in this gene were found in wild soybean. This research will be of interest to plant scientists interested in understanding the genetic control of mophological traits.
Technical Abstract: Determinacy is an agronomically important trait associated with the domestication in soybean (Glycine max). Most soybean cultivars are classifiable into indeterminate and determinate growth habit, while Glycine soja, the wild progenitor of soybean, is indeterminate. Indeterminate (Dt1) and determinate (dt1) genotypes, when mated, produce progeny that segregate in a monogenic pattern. Here, we show that Dt1 is one of the quadruplicated genes that are orthologous to Arabidopsis terminal flower 1 (TFL1), a regulatory gene encoding a signaling protein of shoot meristems. The transition from indeterminate to determinate types in soybean is shown to be the result of independent human selections of four distinct single-nucleotide substitutions in the Dt1 gene, each of which led to a single amino acid change. No amino acid substitutions in Dt1 were found in any of the G. soja accessions collected from different geographic regions, suggesting that this gene was under purifying selection. Genetic diversity of a mini-core collection of Chinese soybean landraces assessed by SSR markers and allelic variation at the Dt1 locus suggest that human selection for determinacy took place at early stages of landrace radiation. Introducing the Dt1 allele into a determinate-type (tfl1) Arabidopsis mutant fully restored the wild-type (TFL1) phenotype, indicating that Dt1 complements the functions of TFL1 in Arabidopsis. Introducing the dt1 allele into the Arabidopsis mutant had no affect. However, the Dt1 homoeolog, despite its more recent divergence from Dt1 than from TFL1, appears to be sub- or neo-functionalized, as revealed by the differential expression of the two genes at multiple plant developmental stages and by allelic analysis at both loci.