Identification of differentially expressed genes between developing seeds of different soybean cultivars

The soybean plants of two soybean varieties Minsoy and Archer and two recombinant inbred lines from the cross that are similar in maturity but differ in yield were grown in St Paul, Minnesota during the summers of 2007 and 2008. In 2007, each line was planted as a single row. In 2008, a randomized complete block (RCB) design was used and each line had 3 replicates planted 1-2 weeks apart. Within each replicate, two rows per line were planted. Seeds were harvested at three developmental stages, namely, seed length = 2 mm, 3.5 mm, and 5-6 mm, which correspond approximately to soybean reproductive stages R4, R5 and early R6, respectively. In 2007 three independent samples were collected for each line and developmental stage. In 2008, two seed samples (one from each row) were collected for each line at each stage within each replicate. The pairs of seed samples were then pooled. Thus, three sets of independent tissue samples were collected for RNA extraction and hybridization on Affymetrix microarrys.