UC San Diego

The plant cuticle is a waxy, hydrophobic coating found on all aerial non-woody plant tissue and serves as a physical barrier protecting the plant from environmental stresses including pathogen infection, dehydration, and UV radiation. Studies on the plant cuticle in various plant model systems show differences in ultrastructure and chemical composition across different plant species, and even within a species, depending on many factors: organ identity, developmental stage and growth conditions. Little functional analysis has been performed to characterize the cuticle’s relationship to pathogen resistance in adult Zea mays, thus leaving the agronomic impact of the cuticle on the adult-stage plant health largely unknown. Maize glossy mutants have defects in cuticle production—examples include lines with impaired levels of lipid biosynthesis or wax transport proteins, making them effective tools to study the cuticle’s impact on pathogen resistance.

In this study, we take a panel of glossy mutants and observe their differences in early stages of pathogen resistance to Cochliobolus heterostrophus and Colletotrichum graminicola, causal agents of Southern Leaf Blight and Anthracnose Stalk Rot, respectively. After establishing methods to observe and quantify GFP-labelled strains of these fungal infections on adult plants, which include fungal adhesion and long-term visual lesion formation, we detected differences in pathogenicity and cuticle wax profiles among our tested glossy mutants by utilizing epifluorescence microscopy, fungal quantification and gas chromatography/mass spectrophotometry. Combined with preliminary data on fungal penetration with confocal microscopy, these results will guide further investigation in elucidating the relationship between adult maize cuticle and pathogen resistance.