Validation of the expression profiles of selected genes in compression and opposite developing xylem. Equal amounts of total RNA isolated from compression (Cx) and opposite (Ox) differentiating xylem from adult maritime pine trees were size fractioned by electrophoresis and transferred to nylon membranes. PCR-amplified cDNA from 21 genes identified as differentially expressed in analyses of cDNA microarray 1 (a) or cDNA microarray 2 (b) were labeled with 32P and used as probes. The panel 13-7 XL A6 shows the result of hybridization with cDNA from a gene classified as non-differentially expressed by the microarray analyses. Panels below every northern blot show methylene blue staining, as a loading control. Functional annotation and accession number of the corresponding ESTs: CS (chorismate synthase, BX250851), DHQ/SDH (3-dehydroquinate dehydratase/shikimate 5-dehydrogenase, BX251808), mSHMT (mitocondrial serine hydroxymethyltransferase, BX249820), EFE (ethylene-forming enzyme, BX251740), LAC (laccase, BX252150), GST (glutathione S-transferase, BX250376), MS (methionine synthase, BX255477), SAMS (S-adenosylmethionine synthetase, BX248790), GS1b (glutamine synthetase 1b, BX253698), GLP (germin-like protein, FN256510), XGT (xyloglucan galactosyltransferase, FN256497), LHT (lysine/histidine transporter, FN256535), PLR (pinoresinol-lariciresinol reductase, FN256693), GDCH (glycine decarboxylase complex H-protein, FN256878), COMT (caffeate O-methyltransferase, FN256925), CCoAOMT (caffeoyl-CoA-O-methyltransferase, FN256577), cSHMT (cytosolic serine hydroxymethyltransferase, FN256831), SAHH (S-adenosyl homocysteine hydrolase, FN256791),unknown (unknown-function gene, FN256975), XET (xyloglucan endotransglucosylase/hydrolase, FN256785), 13-7XLA6 (cDNA of a gene with the same level of expression in Cx and Ox according to microarray analyses).