Tiling microarray of Oryza sativa japonica at 46nt resolution

This experiment was designed to identify transcribed regions of japonica subspecies of the rice genome. A series of high-density oligonucleotide tiling arrays that represent sense and antisense strands of the entire nonrepetitive sequence of all the 12 chromosomes were designed to measure genome-wide transcription. A total of 12253842 36mer oligonucleotide probes positioned every 46 nt on average were used for this purpose. The probes were synthesized via maskless photolithography at a feature density of approximately 389,000 probes per slide. The arrays were hybridized with fluorescence-labeled cDNA reverse-transcribed from equal amounts of four selected poly(A)+ RNA population (seedling root, seedling shoot, panicle, and suspension cultured cells). Keywords: tiling array, genome-wide transcription The arrays were hybridized with fluorescence-labeled cDNA reverse-transcribed from equal amounts of four selected poly(A)+ RNA population (seedling root, seedling shoot, panicle, and suspension cultured cells). The four RNA population from seedling roots, seedling shoots, panicles, and suspension-cultured cells were pooled in equal amount and cDNAs were derived from the RNA mixture. Total RNA and mRNA were isolated using the RNeasy Plant Mini kit (Qiagen, Valencia, CA) and the Oligotex mRNA kit (Qiagen), respectively. First-strand cDNA was generated from 4 micro gram poly(A)+ RNA with SuperScript II reverse transcriptase (Invitrogen, Carlsbad, CA). The cDNAs were precipitated in ethanol:isopropanol (1:1 v/v) and resuspended in 0.1 M NaHCO3 to facilitate coupling of Alexa Fluor 555 NHS esters (Molecular Probes, Eugene, OR) to the reactive groups of the amino-allyl dUTPs and were purified with CyScribe GFX glass fiber spin columns (Amersham Bioscience, Piscataway, NJ). Microarrays were hybridized with 4 ¦Ìg labeled cDNA in 300 micro litre hybridization buffer (50 mM MES, 0.5 M NaCl, 10 mM EDTA, and 0.005% (v/v) Tween-20) for 16 hours at 50 deg C in disposable adhesive chambers (Grace BioLabs, Bend, OR) in a hybridization oven with constant agitation. Hybridized arrays were washed on an orbital Sample in non-stringent buffer (6¡Á SSPE, 0.01% [v/v] Tween-20) for 10 minutes at room temperature, then in stringent buffer (100 mM MES, 0.1 M NaCl, 0.01% Tween-20) for 30 minutes at 45 deg C. This was followed by a 5-minute wash in non-stringent buffer and a 2-minute wash in 0.1X SSC. The arrays were dried with compressed nitrogen and scanned with an Axon 4000B laser scanner at 5 micro meter resolution. The fluorescence intensity data were extracted with the NimbleScan software (NimbleGen Systems, Madison, WI).