Comparison of transcript profiling on Arabidopsis microarray platform technologies.

To date there have been few systematic studies comparing the results of transcript profiling from different microarray platform technologies. We evaluated in detail two different Arabidopsis thaliana microarray platforms: our own Genomic Amplicon arrays and the Qiagen long oligonucleotide arrays designed by Operon; furthermore, we cross-validated these arrays against the Affymetrix AG and ATH1 GeneChips. Data were obtained from all three platforms in each of two separate experiments; (1) at 2 h and (2) 8 h following a salicylic acid treatment applied to both wild-type and npr1-3 mutant plants. A total of 20 hybridizations were performed, analyzing the expression of 26,814 unique locus IDs. We demonstrate that intensity rank is a key variable that affects both inter-platform and cross-platform reproducibility. Although general agreement between platform technologies is low, data derived from high signal intensities (90th percentile) can correlate as well between differing platforms as replicates within the same platform (r=0.4-0.7). We also show that the identification of differentially expressed genes by significance analysis of microarrays is influenced by signal intensity and that overlap between significant gene lists from different platform technologies was as high as 67% when low intensity values were removed. Validation of 41 genes by Northern blot hybridization showed that all platform technologies performed well, qualitatively confirming 83-100% of differential gene expression. Our results suggest that the potential for the broad integration of microarray data from different platforms and laboratories is promising.