title: RNA-seq of Zea mays: primary root 10-12 cm length
design: Seeds of the maize inbred lines B73, A554, H84, H99, Mo17, Oh43, W64A and F1-hybrids B73xA554, B73xH84, B73xH99, B73xMo17, B73xOh43 and B73xW64A were surface sterilized and germinated in moist germination paper. The primary roots of the seedlings were harvested at three developmental stages, i.e. with a length of 2-4 cm, 6-8 cm and 10-12 cm. Samples were harvested in four biological replicates, each sample consists of 10 pooled primary roots resulting in 180 distinct samples (13 genotypes x 3 developemntal stages x 4 replicates). The total RNA of pooled root samples was isolated with the RNeasy Plant Mini Kit (Qiagen, Venlo, The Netherlands). RNA quality was assessed via a Bioanalyzer (Agilent RNA 6000 Pico Chip, Agilent Technologies, Santa Clara, USA). For all samples, a RIN ? 8.9 detected. For each of the 180 samples, 20 ng high quality RNA was used for cDNA synthesis and ampli?cation. cDNA synthesis and libraries for Illumina sequencing were constructed according to the protocol of the manufacturer (TruSeq RNA Sample Preparation, Illumina, San Diego CA, USA). For sequencing, each library was indexed by an Illumina TruSeq Adapter. Indexed libraries were loaded in nine lanes of two flow cell with 20 pooled libraries per lane. Cluster preparation and pair-end read sequencing were performed according to the manufacturer?s instructions (HiSeq 2000, Illumina, San Diego CA, USA).