The PiceaGenExpress database reveals tissue preferential and conserved expression patterns within three gene families. A: Cellulose synthases. B: Photosystem I and II proteins. C: Ubiquitins. NA: Not detected. Tissues: B (Vegetative buds), F (Foliage), X-M (Xylem - mature), X-J (Xylem - juvenile), P (Phelloderm), R (Adventitious roots), M (Megagametophytes), E (Embryogenic cells).