Genotype: RL4452, Age: developing seed 5 days after anthesis
spikes were tagged when anthers were visible, enough developing seeds to fill a 2mL tube were isolated from each spike 5 days after tagging and flash frozen in liquid nitrogen
The 39 lines and parental lines were grown as 1.47 m rows in three replications in a 7x7 (49 entry) lattice design at Winnipeg, Manitoba in 2004. Each replicate had a unique randomization
Total RNA was extracted from frozen seed using a modification of the protocol described at Montana State University Plant Sciences website. The content of a 2 mL tube full of frozen seeds was ground to a fine powder in liquid nitrogen using a mortar and pestle. Ground seed was transferred to 50 mL Oak Ridge tubes and 7.5 mL of extraction buffer was added. [50 mL Extraction Buffer contained 35 mL nuclease-free water, 2.5 mL 1M Tris, pH 9.0. 5 mL 2M NaCl, 5 mL 10% Sarcosyl, 2 mL 0.5M EDTA, pH 8.0, 250 μL 1M DTT]. After vortexing well, 3.75 mL phenol and 3.75 mL chloroform/isoamyl alcohol (49:2) were added and samples vortexed again. Samples were centrifuged 10 min at 13,000 rpm in a Sorvall model RC5C at 4°C using an SS-34 rotor. A total of 7.5 mL of the upper aqueous phase was transferred to a clean Oak Ridge tube, 15 mL Trizol was added and the sample was vortexed. A volume of 3 mL of choloroform was added and the sample was vortexed again. Samples were centrifuged 10 min at 13,000 rpm in the Sorvall at 4°C. A volume of 15 mL of the upper aqueous phase was transferred to a fresh Oak Ridge tube and 10 mL of chloroform was added and the sample was vortexed. Samples were centrifuged again in the Sorvall at 13,000 rpm for 10 min at 4°C. A volume of 12 mL of the upper phase was transferred to a fresh Oak Ridge tube and the RNA precipitated by adding 1,200 uL of 3M sodium acetate and 24 mL of absolute ethanol. Samples were left at -80°C overnight then centrifuged at 14,000 rpm at 4°C in the Sorvall for 20-30 minutes to precipitate the RNA. The pellet was rinsed with 70% ethanol, lightly dried and re-suspended in 1 mL of nuclease-free water. RNA concentration was quantified using a spectrophotometer. All solutions and equipment used in this procedure were RNAse-free. Messenger RNA was enriched from total RNA using the Poly(A) Purist MAG kit (Ambion) according to the protocol provided by the manufacturer. Messenger RNA was checked for quality and quantified by micro-chromatography using an Agilent 2000 Bioanalyzer and the RNA 6000 Nano Assay Kit both purchased from Agilent Technologies . Quantification was carried out according to the instructions provided with the kit.
Biotinylated cRNA were prepared according to the standard Affymetrix protocol (Expression Analysis Technical Manual, Affymetrix). mRNA was used for first and second strand cDNA synthesis using the One Cycle cDNA Synthesis Kit (Affymetrix) following the manufacturers instructions. The resulting cDNA was purified using the GeneChip Sample Cleanup Module (Affymetrix) according to instructions and then used to make purified biotin labelled cRNA using the GeneChip IVT labelling kit and the GeneChip Sample Cleanup Module (Affymetrix). The resulting labelled cRNA was quantified and the yield and size distribution of labelled fragments checked by electrophoresis using the Agilent Bioanalyzer. The labelled cRNA was fragmented using the GeneChip Sample Cleanup Module (Affymetrix) and stored at -20°C.
Following fragmentation, the labelled samples were mixed with 0.1 mg/ml sonicated herring sperm DNA in hybridization buffer (100mM 2-N-morpholino-ethane-sulphonic acid (MES), 1 M NaCL, 20mM EDTA, 0.01% Tween 20, 0.5 mg/ml BSA, 10% DMSO), denatured at 99°C for 5 min then added to GeneChip Wheat Genome Array (Affymetrix) according to manufacturer instructions and hybridized for 16 h at 45°C in a rotisserie oven at 60 rpm. Following hybridization the arrays were washed and stained in the Affymetrix fluidics station 450 according to standard protocol (Section 2.3.3 of the Expression Analysis Technical Manual
GeneChips were scanned using the Affymetrix scanner 3000.
Gene expression data from field grown developing seeds 5 days after anthesis
The raw data in the Affymetrix CEL files of all 4 parental arrays representing two biological replicates of each of two parental genotypes were subjected to quantile normalization using Robust Multi-Array Average (RMA) (Bolstad, B.M., Irizarry, R.A., Astrand, M., Speed, T.P. 2003. A comparison of normalization methods for high density oligonucleotide array data based on variance and bias. Bioinformatics 19:185-193) followed by normalization to the median.