Plastids are small organelles equipped with their own genomes (plastomes). Although these organelles are involved in numerous plant metabolic pathways, current knowledge about the transcriptional activity of plastomes is limited. To solve this problem, we constructed a plastid tiling microarray (PlasTi-microarray) consisting of 1629 oligonucleotide probes. The oligonucleotides were designed based on the cucumber chloroplast genomic sequence and targeted both strands of the plastome in a non-contiguous arrangement. Up to 4 specific probes were designed for each gene/exon, and the intergenic regions were covered regularly, with 70-nt intervals. We also developed a protocol for direct chemical labeling and hybridization of as little as 2 micrograms of chloroplast RNA. We used this protocol for profiling the expression of the cucumber chloroplast plastome on the PlasTi-microarray. Owing to the high sequence similarity of plant plastomes, the newly constructed microarray can be used to study plants other than cucumber. Comparative hybridization of chloroplast transcriptomes from cucumber, Arabidopsis, tomato and spinach showed that the PlasTi-microarray is highly versatile.
The phylogenetic relationships between Tc1 transposable elements have previously been reported for the genomes of some fish species. However, research in this field has been hindered by the low number of fish genome sequences available in databases. The application of a DNA microarray as a universal tool for Tc1 transposon sequence analysis in fish genomes is described here. A prototype oligonucleotide microarray was constructed and used to compare samples of genomic DNA isolated from selected fish species. These results, combined with earlier reported molecular analysis of Tc1 showed the usefulness of DNA microarray in the screening of transposon sequences.
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