Effect of heterozygous deletions on phenotypic changes and dosage compensation in Arabidopsis thaliana

Heterozygous deletions, which include a large number of genes, are often caused by the induction of mutations. The induction of gene dosage compensation should be considered when assessing the effects of heterozygous deletions on phenotypic changes. This mechanism is known to balance the expression levels of genes with different copy numbers in sex chromosomes, but it is also known to operate in autosomes. In the present study, 12 Arabidopsis thaliana BC1 mutants with heterozygous deletions were produced by crossing wild-type Col-0 plants with mutants induced by heavy ion beams. The sizes of the deletions ranged from 50.9 kb to 2.03 Mb, and the number of deleted genes ranged from 8 to 92. Nine of the 12 BC1 mutants showed phenotypic changes in fresh weight 14 days after cultivation or during the flowering period. RNA-sequencing (RNA-seq) analyses of 14-day-old leaves, 40-day-old leaves, and flower buds showed that dosage compensation did not occur in any stage or tissue tested. These results indicate that heterozygous deletions cause phenotypic changes owing to the absence of dosage compensation. Article SummaryIn this study, we examined the impact of heterozygous deletions in Arabidopsis thaliana. By crossing wild-type Col-0 plants with mutants induced by heavy ion beams, we created 12 BC1 mutants, each having heterozygous deletions. The deletions ranged from 50.9 kb to 2.03 Mb, affecting 8 to 92 genes. Nine mutants showed changes in fresh weight or flowering time. RNA-seq analyses of leaves and flower buds revealed no gene dosage compensation. Our findings indicate that phenotypic changes result from the lack of dosage compensation in heterozygous deletions.