Long noncoding miRNA gene represses wheat β-diketone waxes.

The cuticle of terrestrial plants functions as a protective barrier against many biotic and abiotic stresses. In wheat and other Triticeae, β-diketone waxes are major components of the epicuticular layer leading to the bluish-white glaucous trait in reproductive-age plants. Glaucousness in durum wheat is controlled by a metabolic gene cluster at the () locus and a dominant suppressor () on chromosome 2B. The wheat D subgenome from progenitor contains and paralogs on chromosome 2D. Here we identify the gene from durum wheat and demonstrate the unique regulatory mechanism by which acts to suppress a carboxylesterase-like protein gene, , within the multigene locus. is a long noncoding RNA (lncRNA) containing an inverted repeat (IR) with >80% identity to The transcript forms a miRNA precursor-like long hairpin producing a 21-nt predominant miRNA, miRW1, and smaller numbers of related sRNAs associated with the nonglaucous phenotype. When was introduced into glaucous bread wheat, miRW1 accumulated, and its paralog were down-regulated, and the phenotype was nonglaucous and β-diketone-depleted. The IR region of has >94% identity to an IR region on chromosome 2 in that also produces miRW1 and lies within the marker-based location of We propose the loci arose from an inverted duplication of and/or in ancestral wheat to form evolutionarily young miRNA genes that act to repress the glaucous trait.