Conserved signalling components coordinate epidermal patterning and cuticle deposition in barley

The leaf epidermis is sealed by a lipid-rich cuticle to prevent water loss and interspersed with stomatal pores to allow gas exchange. Here the authors provide evidence that two barley proteins, HvYDA1 and HvBRX-Solo, regulate both processes linking epidermal patterning with cuticular properties in a cereal crop. Faced with terrestrial threats, land plants seal their aerial surfaces with a lipid-rich cuticle. To breathe, plants interrupt their cuticles with adjustable epidermal 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 (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 revealed epistatic and modifying relationships between HvYDA1 and HvBRX-Solo, intimating 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 the land plant epidermis in a cultivated cereal.

Automated summary

The study reveals the role of two barley proteins HvYDA1 and HvBRX-Solo in regulating cuticular properties and epidermal patterning. These proteins control the spacing and identity of epidermal cells, as well as the integrity of the cuticle and stomatal patterning in barley. Genetic analyses indicate that HvYDA1 and HvBRX-Solo have epistatic and modifying relationships, suggesting their involvement in interacting pathways linking epidermal patterning with cuticular properties in barley.