Conserved signalling components coordinate epidermal patterning and cuticle deposition in barley

Faced with terrestrial threats, land plants seal their aerial surfaces with a lipid-rich cuticle. To breathe, plants interrupt their cuticles with adjustable pores, called stomata, that regulate gas exchange, and develop other specialised epidermal cells such as defensive hairs. Mechanisms coordinating epidermal features remain poorly understood. Addressing this, we studied two loci whose allelic variation causes both cuticular wax-deficiency and misarranged stomata in barley, identifying the underlying genes, Cer-g/ HvYDA1, encoding a YODA-like (YDA) MAPKKK, and Cer-s/ HvBRX-Solo, encoding a single BREVIS-RADIX-Like (BRX) domain protein. Both genes control cuticular integrity, the spacing and identity of epidermal cells, and barley's distinctive epicuticular wax blooms, as well as stomatal patterning in elevated CO2 conditions. Genetic analyses reveal epistatic and modifying relationships between HvYDA1 and HvBRX-Solo inferring that their products participate in interacting pathway(s) linking epidermal patterning with cuticular properties in barley. This may represent a mechanism for coordinating multiple adaptive features of land plant epidermises in a cultivated cereal. The data involved in this study includes Illumina sequence from exome capture, RNA-Seq and whole genome shotgun sequencing (WGS).