A novel WD40-repeat protein involved in formation of epidermal bladder cells in the halophyte quinoa

Halophytes are plants that grow in high-salt environments and form characteristic epidermal bladder cells (EBCs) that are important for saline tolerance. To date, however, little has been revealed about the formation of these structures. To determine the genetic basis for their formation, we applied ethylmethanesulfonate mutagenesis and obtained two mutants with reduced levels of EBCs ( rebc ) and abnormal chloroplasts. In silico subtraction experiments revealed that the rebc phenotype was caused by mutation of REBC , which encodes a WD40 protein that localizes to the nucleus and chloroplasts. Phylogenetic and transformant analyses revealed that the REBC protein differs from TTG1, a WD40 protein involved in trichome formation. Furthermore, rebc mutants displayed damage to their shoot apices under abiotic stress, suggesting that EBCs may protect the shoot apex from such stress. These findings will help clarify the mechanisms underlying EBC formation and function. Tomohiro Imamura et al. report that a WD40 protein REBC, which differs from the trichome formation-linked WD40 protein TTG1, plays a critical role in epidermal bladder cell formation in quinoa. They further reveal a protective role of the epidermal bladder cells against the shoot apex damage by abiotic stress, especially salt stress, shedding light on the mechanisms underlying epidermal bladder cell formation and function.