Regulatory crosstalk between microRNAs and hormone signalling cascades controls the variation on seed dormancy phenotype at Arabidopsis thaliana seed set.

KEY MESSAGE: We employed an Illumina sequencing approach to identify candidate microRNA cohorts that may greatly contribute to seed dormancy modulation and to construct a microRNA-gene regulatory network in hormone signalling cascades. MicroRNAs (miRNAs) are important signalling molecules and regulate many developmental programs of plants. Some miRNAs have been integrated into gene regulatory networks (GRNs) and coordinate developmental plasticity, but few study systematically investigated how phenotypical variations are regulated through differential expression of miRNA tags in GRNs during seed set. Using 'top-down' analyses (i.e., identify miRNAs associated with known phenotypical variations), we chose two Arabidopsis ecotypes (Cvi-0 and Col-0) with contrasting seed dormancy and sequenced miRNA reads in the first ten phases at seed set. We computationally predicted target genes of miRNAs and implemented statistical analyses for normalized relative expression of top abundant miRNA cohorts between the two ecotypes. We especially focused on miRNA cohorts targeting mRNAs encoding transcription factors in hormone signalling cascades. We report, with high confidence hits, that a cohort of 14 miRNAs (miR-156b, -159b, -160, -161*, -319a, -390a, -396, -773a, -779, -842, -852, -859, -1886*, and a novel sequence in miR8172 family) may greatly contribute to seed dormancy modulation, of which seven are involved in hormone signalling cascades. Moreover, their expression patterns indicated that 5 ± 1 days after flowering (at embryogenesis-to-maturation transition) is a critical phase at seed set. This study reinforces the notion that miRNAs that regulate seed dormancy modulation and provides a novel paradigm of studying the correlation between genotypes (miRNAs) and phenotypes.