To develop heterologous microarrays for closely related non-model systems:
The microarray is a hybridization-based technology. One can utilize a microarray developed for a model system for closely related species by cross-species hybridization. The balance of the specific and non-specific hybridization determines the feasibility of such a heterologous system. The hybridization efficiency, which is used to indicate the abundance level of the hybridized transcripts, is determined by sequence similarity and abundance of the hybridizing targets. To eliminate the noise contributed by the sequence variations, genomic DNA can be labeled (Winzeler et al., 1998) and applied to an array to identify useful probes, which commonly hybridize to both model species and close relatives (Fig. 4). Using such an approach, a large portion of the probes was found to be usable to detect gene expression in maize (90%, Fig. 4), and barley (82%) within the rice GeneChip array. Alterations in gene expression of landmark genes, such as genes encoding GAMyb and a-amylases, were detected in barley aleurone cells after applying plant hormones such as gibberellin or abscisic acid. The uses of genome arrays to non-model crops broaden its applications.