The ethylene-responsive transcription factor CsESR1 positively regulates cucumber ( Cucumis sativus L.) Trichomes

Abstract

Trichomes are multicellular, non-glandular structures that play important roles in plant development, and provide protection against harmful ultraviolet radiation, insect damage and excessive water loss through transpiration. However, the regulation of trichome formation in cucumber remains incompletely understood. Although the phenotype of gl2 have been identified, no fine mapping and candidate gene for it has been determined so far. In this study, CsGL2 was mapped to a 72.5-kb region on chromosome 2, and via fine-mapping, an ethylene-responsive transcription factor ESR1, was identified as the candidate gene. We generated a CRISPR/Cas9 knockout mutant CsGL2  CRwhich was phenotypically resembled the natural gl2 mutant, demonstrating that CsESR1 is CsGL2. We further investigated whether CsGL2 interacts with CsGL1 and CsGL3, two known regulators of trichome development. Our results showed that CsGL2 directly binds to the promoter of CsGL1 and regulates its expression. Moreover, CsGL1 directly interacts with the CsGL3 protein. Genetic analysis demonstrated that CsGL3 is epistatic to CsGL1 and CsGL2, respectively. In conclusion, this study identified CsGL2 as a novel regulator of trichome development in cucumber, which is the first report of an ethylene-responsive transcription factor involved in cucumber trichome development. Furthermore, we elucidate the functional relationships among CsGL2, CsGL1 and CsGL3, providing new insights into the molecular network governing trichome development in cucumber.