title: Plant hormones including ethylene are recruited in calyx inflation in Solanaceous plants.
abstract: Plant hormones direct many processes of floral and post-floral morphogenesis in Angiosperms. However, their role in shaping floral morphological novelties, such as inflated calyx syndrome (ICS) exhibited by a few genera of the Solanaceae, remains unknown. In Withania and Physalis, sepals resume growth after pollination and encapsulate the mature fruit to form a balloon-like structure, i.e. ICS. The epidermal cells of calyx show enlargement and lobation post-fertilization. Application of hormones to depistillated flower buds of Withania revealed that cytokinins and gibberellins mimic fertilization signals. The ICS development is a synchronous step with fruit development; both processes are under the control of more or less the same set of hormones, including cytokinins and gibberellic acids. Interestingly, inhibition of ethylene in the system is sufficient to yield inflated calyx in Withania. In contrast, Tubocapsicum, a closely related species and an evolutionary natural loss mutant of ICS - showed no response to applied hormones, and ethylene led to inflation of the receptacle indirectly. In addition to hormones, the expression of an MPF2-like MADS-box transcription factor in sepals is essential for ICS formation. Nevertheless, the interactions between MPF2-like genes and hormones are barely detectable at the transcript level. Our data provide insight into the role of hormones in generating floral morphological diversity during evolution.
authors.affiliation: Department of Molecular Plant Genetics, Max-Planck-Institute for Plant Breeding Research, Carl-von-Linné-Weg 10, 50829 Cologne, Germany. khan@mpiz-koeln.mpg.de
authors.forename: Muhammad Ramzan
authors.initials: MR
authors.lastname: Khan
authors.forename: Jinyong
authors.initials: J
authors.lastname: Hu
authors.forename: Chaoying
authors.initials: C
authors.lastname: He
mesh_terms: D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics; D003583:Cytokinins / Q000378:metabolism; D005030:Ethylenes / Q000378:metabolism* / Q000494:pharmacology; D005306:Fertilization / Q000187:drug effects; D035264:Flowers / Q000033:anatomy & histology* / Q000166:cytology / Q000502:physiology / Q000648:ultrastructure; D005638:Fruit / Q000187:drug effects / Q000502:physiology; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant / Q000235:genetics; D005875:Gibberellins / Q000378:metabolism; D008954:Models, Biological; D019441:Plant Epidermis / Q000166:cytology / Q000648:ultrastructure; D010937:Plant Growth Regulators / Q000378:metabolism* / Q000494:pharmacology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D054817:Pollination / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D019657:Solanaceae / Q000033:anatomy & histology* / Q000166:cytology / Q000502:physiology / Q000648:ultrastructure; D013045:Species Specificity; D032341:Withania / Q000033:anatomy & histology / Q000166:cytology / Q000502:physiology / Q000648:ultrastructure
chemical_list: D003583:Cytokinins; D005030:Ethylenes; D005875:Gibberellins; D010937:Plant Growth Regulators; D010940:Plant Proteins; C036216:ethylene