SRA

Genomic imbalance caused by varying the dosage of individual chromosomes or chromosomal segments (aneuploidy) has more detrimental effects than altering the dosage of complete chromosome sets (ploidy). Previous analysis on RNA-sequencing data of varied dosage of various chromosomal regions in maize (Zea mays) revealed global modulation of gene expression both on the varied chromosome (cis) and the remainder of the genome (trans). Dysregulation of microRNA (miRNA) dosage has been reported to have profound deleterious effects in many species. miRNAs are preferentially retained as duplicates following whole-genome duplication in grass species and are postulated to be dosage-sensitive. However, little is known regarding the role of miRNAs under genomic imbalance. We examined the impact of increased and/or decreased dosage of 1 interstitial and 19 distal chromosomal regions in concert with a whole-genome ploidy series of haploid, diploid, triploid, and tetraploid via small RNA-sequencing of diploid and haploid maize mature leaf tissue to investigate the impact of aneuploidy and polyploidy on expression of miRNAs. In general, cis miRNAs in aneuploids present a predominant gene-dosage effect, whereas trans miRNAs trend toward the inverse level, although other types of responses including dosage compensation, increased effect, and decreased effect also occur. Significant correlations between expression levels of miRNAs and their targets were identified in aneuploids, indicating the regulatory role of miRNAs on gene expression triggered by genomic imbalance. The findings provide novel insights into understanding of gene balance from the aspect of the function of miRNAs. Overall design: Small RNA sequencing was performed to the maize mature leaf tissue of a collection of 20 maize B-A translocation lines created by translocations between the normal chromosomes and the supernumerary B chromosome containing various copies of chromosomal segments covering 82.1% of the maize W22 genome, in concert with a whole-genome ploidy series of haploid, diploid, triploid and tetraploid lines.