Transcript profiling in plastid arginine tRNA-CCG gene knockout moss: construction of Physcomitrella patens plastid DNA microarray.

The moss Physcomitrella patens is a newly established model plant that is widely used for the characterization of gene function by targeted gene knockout or over-expression. The target gene disruption occurs in both the nuclear and chloroplast genomes. We applied DNA microarray technology to the P. patens plastid genome for large-scale analysis of transcripts. A microarray was constructed containing 108 DNA fragments to detect all annotated plastid genes. We analyzed the transcript profile in a knockout transformant for the arginine tRNA gene, trnR-CCG, and confirmed previous results that rbcL and psaI transcripts accumulate in similar levels to wild-type moss, and accD transcript level is higher than those of wild-type moss. Additionally, the plastid DNA microarray revealed that most plastid genes were expressed at similar levels in wild-type and transformant mosses. This indicates that trnR-CCG is not essential for the expression of plastid genes.