Barley BODYGUARD controls cuticular specialisations regulated by SHINE transcription factors
Land plants secrete a protective outer cuticular layer which has diverse functions  and composition depending on species, stage and tissue. Barley develops a late-stage ß-diketone wax bloom, common in Poeceae species, on its leaf sheaths, stems and spikes, and a grain cuticle which adheres to inner floral hulls, causing barley's distinctive 'covered' grain. Two barley SHINE/WAX-INDUCER transcription factors, HvWIN1 and NUD, promote the wax bloom and hull adhesion, respectively, yet we know little about other genes involved. Leveraging a wax-deficient mutant, we identify the barley BODYGUARD1 (HvBDG1) gene encoding an a/ß-hydrolase as crucial for leaf cuticular integrity and full wax bloom deposition. Mining tetraploid wheat mutant populations demonstrated that BDG1 and WIN1 orthologues also control the wax bloom in wheat. We also discovered that both HvBDG1 and HvWIN1 promote strong hull adhesion by influencing similar grain surface characteristics as NUD. We also reveal an additional role for NUD in leaf cuticle integrity. Comparative analyses suggest that NUD and HvWIN1 may act independently in the grain and leaf, although likely via overlapping targets, including HvBDG1. Altogether, our work greatly expands the genetic and developmental mechanisms underlying shared and distinctive cuticular features in plants.
Land plants secrete a protective outer cuticular layer which has diverse functions  and composition depending on species, stage and tissue. Barley develops a late-stage ß-diketone wax bloom, common in Poeceae species, on its leaf sheaths, stems and spikes, and a grain cuticle which adheres to inner floral hulls, causing barley's distinctive 'covered' grain. Two barley SHINE/WAX-INDUCER transcription factors, HvWIN1 and NUD, promote the wax bloom and hull adhesion, respectively, yet we know little about other genes involved. Leveraging a wax-deficient mutant, we identify the barley BODYGUARD1 (HvBDG1) gene encoding an a/ß-hydrolase as crucial for leaf cuticular integrity and full wax bloom deposition. Mining tetraploid wheat mutant populations demonstrated that BDG1 and WIN1 orthologues also control the wax bloom in wheat. We also discovered that both HvBDG1 and HvWIN1 promote strong hull adhesion by influencing similar grain surface characteristics as NUD. We also reveal an additional role for NUD in leaf cuticle integrity. Comparative analyses suggest that NUD and HvWIN1 may act independently in the grain and leaf, although likely via overlapping targets, including HvBDG1. Altogether, our work greatly expands the genetic and developmental mechanisms underlying shared and distinctive cuticular features in plants.
The James Hutton Institute, Scotland, United Kingdom