The Arabidopsis Genome Oligo Set Version 1.0 (Operon Biotechnologies, Huntsville, AL, USA) consists of 26090 70mer oligonucleotides (http://operon.com/arrays/oligosets_arabidopsis.php). As positive controls, we included oligos for twelve housekeeping genes (Operon). As negative controls, we synthesized four oligonucleotides specific for human genes with no similarity to any Arabidopsis gene and included twelve oligonucleotides with no similarity to any Arabidopsis gene (Operon). We used a PCR amplified green fluorescent protein (GFP) cDNA (Invitrogen, Carlsbad, CA, USA) as an orientation marker. Oligonucleotides were resuspended in 384 well flat bottom plates (Nunc, Rochester, NY, USA) to a concentration of 100 mM in 3 x SSC. Oligos were printed on MicroGrid II robots using Microspot 10k pins (Biorobotics, Huntington, UK) depositing approximately 0.5 nl (0.0075 pmole) of each oligo onto EZ rays aminosilane slides (Apogent Discoveries, Hudson, NH, USA). The pitch of the grid used for this library was 0.2 mm. Oligos were UV cross linked at 3000 x 100 μJ using a UV Stratalinker 2400 (Stratagene, La Jolla, CA, USA). We spotted single spots for 25,792 of the 26090 target oligonucleotides (due to software problems the print run was terminated shortly before completion); in addition, each subgrid contained six replicate spots of each of the four human negative controls, three spots of equally distributed Operon negative controls, a single spot of each of the twelve house keeping controls, and GFP marker on each corner of the s Keywords = GenomeBC-Forestry Keywords = 26k array v.1