Description
The Aristolochia sepal-derived petaloid perianth possesses an inner epidermis with various specialized trichomes related to fly pollination. Different trichomes can be found in each of the three floral portions, namely secretory multicellular filamentous trichomes in the utricle, trapping multicellular conical trichomes in the tube, and three-celled hooked trichomes in the limb. Trichomes inside the perianth are an evolutionary novelty in all species of subgenera Aristolochia (represented here by A. fimbriata and A. ringens) and Pararistolochia, and they are lacking in all species of subgenus Siphisia (represented by A. macrophylla). The molecular mechanisms controlling epidermal cell fate and trichome development have been identified in leaves of the model Arabidopsis thaliana, but remain almost unexplored in floral organs of non-model taxa. Here we study the morpho-anatomical and molecular basis of epidermal elaboration in the perianth of Aristolochia fimbriata, A. ringens, and A. macrophylla, to identify the genetic regulatory network (GRN) underlying multicellular trichome development. We used a candidate gene approach to assess the spatio-temporal expression patterns of GLABRA2 (GL2), GLABRA3 (GL3), TRANSPARENT TESTA GLABRA1 (TTG1), TRIPTYCHON (TRY), transcription repressors MYB5 and MYB6, HOMEODOMAIN GLABROUS 2 (HDG2), MYB106-like (MYB106-like), WAX INDUCER 1 (WIN1), and ETHYLENE RESPONSE DNA BINDING FACTOR (RAV1-like) in A. fimbriata. We found that genes involved in trichome development vary depending on the organ where they are formed. Stem, leaf, and pedicel trichomes recruit most of the transcription factors (TFs) described above. Conversely, floral trichomes only use a subset of genes including AfimGL2, AfimRAV1-like, AfimWIN1, AfimMYB106-like, and AfimHDG2. Lastly, we also identify differentially expressed genes (DEGs) between the limb, the tube, and the utricle of A. fimbriata and the trichome-less species A. macrophylla, putatively linked to epidermal specializations. We re-evaluate the core genetic network shaping trichome fate in flowers of early divergent angiosperms and show a morphologically diverse output with a simpler genetic mechanism in place when compared to the models Arabidopsis thaliana and Cucumis sativus. In turn, our results strongly suggest that only non-floral trichome identity GRN has been maintained over evolutionary time. Finally, this work allows us to propose the first hypothetical GRN underlying floral multicellular trichome development in Aristolochia species.| Period | 11 Oct 2017 |
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| Event title | IX Latin American Society for Developmental Biology Meeting |
| Event type | Other |
| Location | Medellín, ColombiaShow on map |
| Degree of Recognition | International |