Development of the abscission zone

Purpose of review: This review focuses on the genetic mechanisms that underlie differentiation of tissues specialised for cell separation in three well-studied models: the abscission zone (AZ) of the flower and fruit pedicel, floral organ AZ, and the related dehiscence zone of the fruit. Findings: Nearly all research on abscission has concentrated on the activation stage, when cells of the AZ become competent to respond to abscission-promoting signals, or the separation stage, characterised by loss of cell-cell adhesion. There have been relatively few studies on mechanisms responsible for the initial differentiation of the AZ during organ development. The comparable architectures of AZs in various developmental circumstances suggest patterning by analogous mechanisms and involvement of similar activities of genes. Directions for future research: The control of postharvest losses through abscission at the level of AZ development deserves more attention. A mechanistic model for AZ development will require the identification of additional genes, through genetic or molecular approaches, as well as the characterisation of interactions between these genes.