The FUSED LEAVES1/ADHERENT1 Regulatory Module Is Required For Maize Cuticle Development And Organ Separation

Abstract

In land plants all aerial epidermal cells are covered by the cuticle, an extracellular hydrophobic layer. The cuticle represents a primary barrier between cells and the external environment, provides protection against abiotic and biotic stresses, and prevents organ fusion during development. Here we report the cloning and characterization of a classic mutant of maize called adherent1 (ad1), first described a century ago, and we show that AD1 encodes a 3-KETOACYL-CoA SYNTHASE involved in the deposition of cuticular wax on the epidermis of leaves and inflorescences. ad1 mutants show decreased amounts of various wax components as well as a range of organ fusion defects during vegetative and reproductive development. Accordingly, we find that AD1 is strongly expressed in the epidermis of various developing organs where it is directly regulated by the MYB transcription factor FUSED LEAVES1 (FDL1), which in turn controls a series of additional genes involved in cuticle formation. Altogether, our results identify a major pathway of cuticle biosynthesis essential for the development of maize plants, and a key regulatory module that is conserved across monocot and eudicot species. One sentence summaryThe classic maize mutant adherent1, first isolated a century ago, is affected in an enzyme responsible for cuticle formation that is regulated by the MYB transcription factor FUSED LEAVES1.