Expression of Flowering Time Genes in Soybean E1 Gene Isolines.

Control of soybean flowering time is important for geographic adaptation, and maximizing yield. A series of genes (E genes) that condition time to flowering have been identified, however, these E genes have not been sequenced, nor is their mechanism of control of flowering clearly understood.  The E genes are available as near isogenic lines (NILs) making them an excellent model system for studying the flowering pathway genes in soybean.  As an initial attempt to begin characterization of the effects of these genes at the molecular level, two isolines of the E1 gene in the Harosoy background [OT93-5 (e1) and OT93-26 (E1)] obtained from Dr. Elroy Cober (Agriculture and Agri-Food Canada, Ottawa, ON, Canada) were analyzed for plants grown in a growth chamber under long day conditions.  Plants were harvested every three hours over a 72 hour period starting at day 6 post planting.  Preliminary data has indicated that the pre-inductive photoperiod-sensitive phase of the E1 NILs responsible for inducing flowering is perceived in the time period encompassed in the experiment.  Under the long day conditions used the e1 isoline typically flowers in 30 days, while the E1 isoline flowers in 40 days.  RNA was isolated from three individual plants and RNA samples were pooled for each line each time period for cDNA synthesis.  RT-PCR analysis was performed using primers synthesized to a number of putative flowering time genes based on homology of soybean EST sequences to Arabidopsis genes.  Gene expression results for most of the primers were similar to that observed in Arabidopsis suggesting that these EST sequences correspond to the soybean flowering-time homologues.  No major differences in expression levels were observed between the E1 and e1 lines suggesting that E1 gene does not directly affect these flowering genes.