Arabidopsis complementary DNA (cDNA) microarrays were hybridized with labeled cDNA from mature leaves and emerging tillers of wild oat to determine if they could identify gene expression profiles in distantly related species. More than 23% of the > 11,000 cDNAs on the array hybridized to the wild oat probe. Transcription patterns detected by hybridization to the arrays are indicators for physiological processes in the tissues tested. Coordinated expression patterns for these genes in Arabidopsis indicate common signals involved in their regulation. The results demonstrate that probing cDNA-based arrays from well-characterized species can provide valuable insight into the signal transduction processes regulating growth and development of poorly characterized species.