Expression pattern of transcripts encoding water channel-like proteins in Norway spruce (Picea abies)

With the aim of identifying cells and tissues with high expression of aquap orins (water channels) or homologous genes in Norway spruce (Picea abies), we report the expression patterns of such transcripts in seedlings, in root s of various ages, and in needles. In situ hybridization experiments with a conserved area of a tonoplast intrinsic protein (TIP) gene from P. abies g ave high expression signals in differentiating vascular tissues and in the columella cells of the seedling root cap. High-staining signals were also s een in guard cells and in the bundle sheath cells of needles. Moreover, a s lightly increased staining signal was seen in cells forming lateral roots a s well as in adventitious roots formed from hypocotyl cuttings. By using PC R-based procedures we also identified a full-length aquaporin-like cDNA (mi pr) from roots of two-week old seedlings. Sequence homology analysis of the gene suggests that it belongs to the TIP subgroup within the large MIP (ma jor intrinsic protein) family. A phylogenetic analysis of the plant MIP fam ily, including both plasmamembrane (PIP) and tonoplast intrinsic protein (T IP) from Picea, suggests that MIP subgroups evolved already 330 million yea rs ago, as this is the dating of conifer and angiosperm divergence.