Novel cuticle regulators in maize and their impact on abiotic and biotic stress responses
Final Report Abstract
In the first project, a set of maize cuticle mutants were used to characterize the protective capacity of the altered cuticle in dehydration and pathogen response. The most interesting candidate glossy mutants gl11 and gl17 were shown to have an impact on the water barrier capacity of the adult leaf cuticle during dehydration, as well as increased susceptibility to the leaf pathogen Cochliobolus heterostrophus, the causal agent of the agriculturally important crop disease southern leaf blight (SLB). Changes in cuticle composition in these mutants were analyzed by GC-MS. While gl11 showed an overall reduction of cuticle wax content constituted by a reduction in almost all wax classes, gl17 displayed an overall increase in most of the wax classes but a specific reduction in wax esters, suggesting an important role of wax esters for both these protective cuticle features. Identification of the causative mutation for both candidates, gl11 and gl17, is still pending, opening up an avenue of a more detailed characterization and functional cuticle analysis of the adult maize leaf. A second part of the project characterized the relationship of cuticle structure, composition and function of the grass-specific bulliform cells (BCs), an adaxially-located epidermal cell type organized in longitudinal rows along the leaf, which is implicated in the leaf rolling response upon dehydration. We could show that BC cuticles are roughly 4-times thicker than pavement cell cuticles and have a distinct ultrastructure. Biochemical analysis of BC-enriched cuticle tissue revealed mainly differences in cutin monomer content and composition for this cell type, compared to other leaf epidermal cells. With a newly established cryo-imaging method we could show that, upon dehydration, BCs indeed show increased shrinkage compared to other epidermal cells. Additionally, BC-enriched tissue showed higher water loss over the cuticle. We hypothesize that this cell type-specific cuticle, despite its increased thickness, is more water permeable than the epidermal pavement cell cuticle, facilitating increased water loss of BCs upon dehydration and therefore contributing to the function of bulliform cells in stress-induced leaf rolling observed in grasses. Together, our findings advance knowledge of cuticle composition/structure/function relationships, and how cuticle specialization can contribute to cell and organ functions.
Publications
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(2020). Structure-function analysis of the maize bulliform cell cuticle and its role in dehydration and leaf rolling. Plant Direct 4(10), e00282
Matschi S., Vasquez M.F., Bourgault R., Steinbach P., Chamness J., Kaczmar N., Gore M.A., Molina I., Smith L.G.
