Plants undergo a self-pruning mechanism called abscission to detach organs. Efforts to understand this process have been led by studies in a model plant species, Arabidopsis thaliana, in which the outer parts of the flower (sepals, petals, stamens) are shed to make way for the developing fruit. Abscission involves specialized cell layers called the abscission zone (AZ) where separation takes place. When organs detach, newly exposed cells on the plant surface become sealed against water loss and pathogen entry through the formation of a protective layer. Plants in which the protective layer develops slowly or weakly are often susceptible to disease, making the study of this layer of importance to agriculture. The protective layer in Arabidopsis plants is suggested to be a lipid-based, cell wall-associated polymer such as cutin or suberin. To determine the identity of this polymer in Arabidopsis, AZs were harvested and subjected to chemical analysis using gas chromatography with flame ionization and mass spectroscopy methods of detection. This analysis revealed a form of cutin as a primary component of the Arabidopsis protective layer. Knockout mutants in genes encoding key enzymes in the synthesis of this cutin exhibited delay in floral organ abscission and the protective layer was more permeable. These data suggest roles for cutin in organ separation and surface protection.
