Long noncoding miRNA gene represses wheat β-diketone waxes

Significance Higher plants have waxy surface layers that prevent uncontrolled water loss. Many wheat cultivars accumulate diketone epicuticular waxes in reproductive-age plants that produce a glaucous appearance. We identify INHIBITOR of WAX1 ( Iw1 ), a dominant glaucous repressor, as a young miRNA gene (MIRNA) that produces an miRNA, miRW1, which targets the transcript of the biosynthetic gene WAX1-CARBOXYLESTERASE ( W1-COE ) for degradation. The high sequence similarity between the Iw1 hairpin sequence and W1-COE suggests that this MIRNA gene arose from an inverted duplication of its target. The cleavage specificity of miRW1 for its target gene defines the unique role of a young MIRNA gene in the regulation of an important agricultural trait related to stress tolerance.