Dynamic patterns of circular and linear RNAs in maize hybrid and parental lines

Hybrid vigor, also known as heterosis, has been widely utilized in agronomic production of maize (Zea mays L.) and other crops. However, the molecular mechanisms underlying heterosis are still not fully understood. To provide a more complete understanding of the transcriptomic dynamics associated with heterosis, we collected a comprehensive set of sequence data on linear mRNA transcripts and circular RNAs (circRNAs) from seedling leaves of two widely used maize inbred lines and their F₁ hybrid at the V4 growth stage. We detected over 25,000 expressed genes with more than 1200 circRNAs that showed dramatic and distinct variations in expression level across the three genotypes. Although most linear and circular transcripts exhibited additive expression in the hybrid, the expression of circRNAs was more likely to be nonadditive. Interestingly, the levels of linear transcripts and their corresponding circRNAs from the same loci showed a significant relationship and coordinated expression mode across all three genotypes. Notably, in the hybrid, allele-specific expression of linear transcripts was significantly associated with the expression of circRNAs from the same locus, suggesting potential regulatory cross talk between linear and circular transcripts. Our study provides a deeper understanding of dynamic variations for both the linear and circular transcriptome in a classical hybrid triplet of maize.