Genetic mechanisms underlying perianth epidermal elaboration of Aristolochia ringens Vahl (Aristolochiaceae)

Aristolochia species possess a unique sepal-derived petaloid kettle-shaped perianth with distinctive features and epidermal cell types that likely promote pollination. Epidermal cell fate, proliferation, and specialization as well as perianth elaboration have been well studied in core eudicot model species, but little information is available in early diverging angiosperms. Here we study the morpho-anatomical and molecular basis of perianth elaboration of Aristolochia ringens. We detected multicellular-conical trichomes in the expanded limb and the narrow tube, and multicellular, filamentous trichomes in the inflated utricle. Transcriptomic profiling of the limb, the tube and the utricle of A. ringens was analyzed in order to identify differentially expressed genes (DEGs) providing specific features to each perianth portion. Among the DEGs many are involved in plant cell wall development, wax accumulation, and cell proliferation. In the latter category we identified three CINCINNATA TCP transcription factors highly expressed in the limb likely aiding cell proliferation, and a microRNA (Arin-miR319a) targeting ArinCIN1 restricted to the utricle. In addition, we found single copy homologs for several of the key trichome development genes reported for other species. Here, we provide the first comprehensive framework for the study of perianth shaping and elaboration in Aristolochia.