Whole Genome Expression Analysis of near Isogenic Lines for the Soybean E1 Gene Under Short and Long Day Conditions.

Control of soybean flowering time is important for geographic adaptation, and maximizing yield and has been shown in soybean be to be controlled by a series of genes (E genes) that condition time to flowering. 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 camber under short day (SD: 12hr day/12hr dark) and long day (LD: 20hr day/4hr dark) conditions.  Preliminary data has indicated that the pre-inductive photoperiod-sensitive phase of the E1 NILs responsible for inducing flowering is perceived as early as 5-7 d post planting.  Plants were harvested at 11am (4 hr post light initiation) on day 7 post planting.  Microarray analysis was performed using the Affymetrix Glycine max GeneChip on 2 samples of each NIL and light regime.  Analysis was done to compare NIL differences as well as SD vs LD differences.  Fifty-two Affymetrix probe sets were observed to be differentially expressed between the e1 NIL and E1 NIL, however none of the genes identified correspond to a flowering time gene homologue, and neither do they map to the location of the E1 locus on the soybean genome based on the integrated genetic and molecular maps (G. max assembly version 1.01).  RT-PCR analysis was used to confirm differential expression for a number of the genes identified on the microarray.  Analysis is ongoing to dissect the role of these genes in relationship to the E1 locus.