|Thakare, Dhiraj -|
|Kumudini, Saratha -|
Submitted to: Planta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 26, 2011
Publication Date: June 17, 2011
Citation: Thakare, D., Kumudini, S., Dinkins, R.D. 2011. The alleles at the E1 locus impact the expression pattern of two soybean FT-like genes shown to induce flowering in Arabidopsis. Planta. 234:933-943. Interpretive Summary: Control of flowering time is important for geographic adaptation and maximizing yield. Very little is known about the genes that condition flowering response in legumes. Soybean is an excellent model system for legume research as the genome sequence has been released. It has been shown that one of the primary signals inducing flowering is the protein product from Flowering Locus T (or FT) based on the Arabidopsis model. Analysis of the soybean genome has shown that soybean contains ten FT-like genes. We characterized the expression of these ten soybean genes and found that only two of the ten putative FT-like genes were expressed at any significant level. Expression profiles of the genes was tested using reverse transcription-polymerase chain reaction (RT-PCR) procedures on samples isolated every three hours revealed that the two soybean FT-like genes followed the expression profile expected based on the Arabidopsis model. Transformation of both of these soybean FT genes into Arabidopsis mutants defective at the FT locus, showed that both could compliment the Arabidopsis mutant phenotype, thus demonstrating that both can function as the florigenic signal in soybean.
Technical Abstract: A small gene family of phosphatidyl ethanolamine-binding proteins (PEBP) has been shown to function as key regulators in flowering; inArabidopsis thaliana the FT protein promotes flowering whilst theclosely related TFL1 protein represses flowering. Control of flowering time in soybean [Glycine max (L.) Merr.] is important for geographic adaptation and maximizing yield. Soybean breeders have identified a series of loci, the E-genes, that control photoperiod mediated flowering time, yet how these loci control flowering is poorly understood. The objectives of this study were to evaluate the expression of GmFT-like genes in the E1 near-isogenic line (NIL) background. Of the twenty closely related PEBP proteins in the soybean genome, ten are similar to the Arabidopsis FT protein. Expression analysis of these ten GmFT-like genes confirmed that only two are detectable in various conditions tested. Further analysis of these two genes in the E1 NILs grown under short-day (SD) and long-day (LD) conditions showed a diurnal expression and tissue specificity expression commensurate with soybean flowering time under SD and LD conditions, suggesting that these were good candidates for flowering induction in soybean. Arabidopsis ft mutant lines flowered early when transformed with the two soybean genes, suggesting that the soybean genes can complement the Arabidopsis FT function. Flowering time in E1 NILs is consistent with the differential expression of the two GmFT-like genes under SD and LD conditions, suggesting that the E1 locus, at least in part, impacts time to flowering through the regulation of the soybean FT expression.