MOLECULAR EVOLUTION OF A MORPHOLOGICAL NOVELTY IN SOLANACEAE: THE INFLATED-CALYX-SYNDROME (ICS) IN PHYSALIS

C. He, H. Saedler
The Chinese lantern or Inflated-Calyx-Syndrome (ICS) encapsulating the Physalis berry is a morphological novelty in the Solanaceae. ICS is generated by heterotopic expression of MPF2, which encodes a MADS-box transcription factor. RNAi experiments in Physalis and ectopic expression in Solanum suggest that MPF2 promotes sepal cell division and inhibits cell elongation. Heterotopic expression of MPF2 in Physalis floridana is due to promoter alterations as compared to the promoter of its ortholog STMADS16 from the closely related Solanum tuberosum, which does not feature ICS. Clearly, heterotopic expression of MPF2 is not sufficient for ICS formation since signals released from the fertilization process or seed development are also important for calyx growth. Depistillation experiments and subsequent treatment of the flower buds with plant hormones suggest the importance of phytohormones, like cytokinins and gibberellins, for ICS formation, which can substitute the role of pollination signals. Heterotopically expressed MPF2 generates small sepal cells, which could be amplified by cytokinins; gibberellins elongate these cells, thus generating ICS. These findings are corroborated by the synthesis of an ICS-like trait in transgenic Solanum tuberosum via ectopic expression of STMADS16 and treatments with cytokinin or gibberellin. Recruitment of MPF2 from a vegetative context, like STMADS16 in potato, to a floral context, as MPF2 in Physalis, is an important change in the evolution of ICS in the Solanaceae.
He, C. and Saedler, H. (2007). MOLECULAR EVOLUTION OF A MORPHOLOGICAL NOVELTY IN SOLANACEAE: THE INFLATED-CALYX-SYNDROME (ICS) IN PHYSALIS. Acta Hortic. 745, 171-182
DOI: 10.17660/ActaHortic.2007.745.6
https://doi.org/10.17660/ActaHortic.2007.745.6
Chinese lantern, Solanaceae, MADS-box gene MPF2, heterotopic expression, plant hormones, pollination, cytokinin, gibberellin
English

Acta Horticulturae