Class VIIIb APETALA2 Ethylene Response Factors in Plant Development

The APETALA2 (AP2) transcription factor superfamily in many plant species is extremely large. In addition to well-documented roles in stress responses, some AP2 members in arabidopsis, such as those of subgroup VIIIb, which includes DORNRÖSCHEN, DORNRÖSCHEN-LIKE, PUCHI, and LEAFY PETIOLE, are also important developmental regulators throughout the plant life cycle. Information is accumulating from orthologs of these proteins in important crop species that they influence key agronomic traits, such as the release of bud-burst in woody perennials and floral meristem identity and branching in cereals, and thereby represent potential for agronomic improvement. Given the increasing recognition of their developmental significance, this review highlights the function of these proteins and addresses their phylogenetic and evolutionary relationships. The Arabidopsis AP2 ethylene response factor subclass VIIIb transcription factors DORNRÖSCHEN, DORNRÖSCHEN-LIKE, PUCHI, and LEAFY PETIOLE are key developmental regulators throughout the plant life cycle and integrate into multiple hormone response networks. Accumulating functional data for orthologs of these proteins in diverse species implicate roles in bud-dormancy release in response to seasonal cues, the regulation of inflorescence architecture, organ initiation and cell proliferation, meristem function, and shoot regeneration. Phylogenetic analysis reveals that class VIIIb family progenitors existed in mosses. The presence of all class VIIIb proteins in the early angiosperm Amborella trichopoda implies that they execute ancient functional roles that evolved with flowering plants. Genome duplications and neofunctionalization have been accompanied by the loss of some homologs in particular lineages. Selected functions can be potentially applied to improve agronomically important traits in crop plants.