Characterization and functional analysis of gerbera () genes reveal the role of in defense against the root rot pathogen .

Unlabelled: Gerbera (), a major fresh cut flower crop, is very susceptible to root rot disease. Although plant defensins (PDFs), a major group of plant antimicrobial peptides, display broad-spectrum antifungal and antibacterial activities, genes in gerbera have not been systematically characterized. Here, we identified and cloned nine genes from gerbera and divided them into two classes based on phylogenetic analysis. Most Class I genes were highly expressed in petioles, whereas all Class II genes were highly expressed in roots. inoculation strongly upregulated all Class II genes in roots and upregulated all Class I genes in petioles. Transient overexpression of and inhibited infection in tobacco () leaves. Transient overexpression of , but not , significantly upregulated and gene expression in tobacco leaves, indicating that overexpressing activated the jasmonic acid/ethylene defense pathway and that the two types of GhPDFs have different modes of action. Prokaryotically expressed recombinant GhPDF2.4 inhibited mycelial growth and delayed the hyphal swelling of , in vitro, indicating that GhPDF2.4 is a morphogenetic defensin. Moreover, the addition of GhPDF2.4 to plant culture medium alleviated the root rot symptoms of in vitrogrown gerbera seedlings and greatly reduced pathogen titer in -inoculated gerbera roots in the early stages of treatment. Our study provides a basis for the use of GhPDFs, especially GhPDF2.4, for controlling root rot disease in gerbera.

Supplementary Information: The online version contains supplementary material available at 10.1007/s42994-024-00146-8.