Spatiotemporal gene expression profiles associated with male strobilus development in Cryptomeria japonica by suppression subtractive hybridization

To identify the genes associated with the formation and development of the male strobilus of Cryptomeria japonica D. Don (Sugi), male strobilus-specific suppression subtractive hybridization (SSH) libraries were constructed from three different stages of male strobilus development. From these SSH libraries, 1,012 unigene sets including 314 contigs were assembled from 2,448 sequences. The profiles of the genes isolated from the SSH libraries differed strongly according to developmental stage: 49%, 13% and 29% of genes were unique to the early stage (stage E), tetrad stage (stage T), and mature stage (stage M) SSH libraries, respectively. To evaluate the reliability of the SSH libraries, we focused on the eight genes strongly concentrated in the three SSH libraries and performed RT-PCR analysis. All genes tested were expressed more strongly in the male strobilus than in the shoot. Our findings suggest that the gene profiles associated with male strobilus development differ in both number and kind of dominantly expressed genes.