Identification of transcriptome SNPs for assessing allele specific gene expression within a super-hybrid rice Xieyou9308. Oryza sativa

We identified 9325 reliable single nucleotide polymorphisms (SNPs) distributed throughout the genome, of which nearly 68% were represented in R9308 versus Xieqingzao B by CT and GA SNPs. This may indicate that DNA methylation, a heritable epigenetic mark, exists in the parents and their F1 hybrid. Of 2793 identified transcripts with consistent allelic biases, only 480 (17%) showed significant allelic biases during at least one stage, suggesting that trans effects may mediate most transcriptional differences in hybrid offspring. Approximately 67% and 62% of the 480 transcripts showed allelic expression biases towards the R9308 allele at tillering and heading stages, respectively. Transcripts with higher levels of gene expression in R9308 also exhibited R9308 allelic biases in the hybrid. In addition, 125 transcripts were identified with significant allelic expression biases at both stages, of which 74% showed allele expression biases towards the R9308 allele. R9308 alleles may tend to preserve their characteristic states of activity in the hybrid and may play an important role in hybrid vigor at both stages. The allelic expression of 355 transcripts was highly stage-specific, with divergent allelic expression patterns observed at different developmental stages. Many transcripts associated with stress resistance were differently regulated in the F1 hybrid. The results of this study would provide valuable information for further understanding molecular mechanisms of heterosis. Overall design: Root mRNA profiles of a super-hybrid rice Xieyou 9308 and its parents at tillering and heading stages were generated by deep sequencing, in duplicate, on Illumina Hiseq 2000 platform.