Analysis of gene activation during anther development. The transcriptomes of all four anther stages were compared to their preceding stage of development. SAM has been used as the reference for PMA. (a) The number of genes up- or down-regulated ≥ 2-fold at p-value ≤ 0.005 are plotted on the graph. Amongst the up-regulated genes, the numbers that have no detectable expression (GC-RMA value ≤ 10) in any of their previous anther stages as well as non-anther stages have been annotated in maroon boxes in the individual columns as specifically 'triggered'. While such candidates may have expression in later anther stages, expression first appears in that particular anther stage. (b) A bar graph highlighting the distribution of the up-regulated and specifically-triggered genes at individual stages of development into functional categories based on GO annotations.