RESUMO
Piperquinchasense is described and illustrated as a new species occurring in the understory of wet montane forest of the middle Magdalena Valley in Colombia, the easternmost portion of the Chocó Region. Its relationships are discussed with related taxa from the Macrostachys clade. An identification key for 35 Neotropical Piper species with peltate leaves is provided.
ResumenPiperquinchasense se describe e ilustra como una nueva especie que ocurre en el sotobosque de bosques húmedos montanos del valle medio del Magdalena en Colombia, la porción más oriental del Chocó Biogeográfico. Se discuten sus relaciones con otras especies del clado Macrostachys. Se presenta una clave de identificación para 35 especies de Piper Neotropical con hojas peltadas.
RESUMO
BACKGROUND AND AIMS: The epidermis constitutes the outermost tissue of the plant body. Although it plays major structural, physiological and ecological roles in embryophytes, the molecular mechanisms controlling epidermal cell fate, differentiation and trichome development have been scarcely studied across angiosperms, and remain almost unexplored in floral organs. METHODS: In this study, we assess the spatio-temporal expression patterns of GL2, GL3, TTG1, TRY, MYB5, MYB6, HDG2, MYB106-like, WIN1 and RAV1-like homologues in the magnoliid Aristolochia fimbriata (Aristolochiaceae) by using comparative RNA-sequencing and in situ hybridization assays. KEY RESULTS: Genes involved in Aristolochia fimbriata 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 small subset of genes including AfimGL2, AfimRAV1-like, AfimWIN1, AfimMYB106-like and AfimHDG2. The remaining TFs, AfimTTG1, AfimGL3, AfimTRY, AfimMYB5 and AfimMYB6, are restricted to the abaxial (outer) and the adaxial (inner) pavement epidermal cells. CONCLUSIONS: We re-evaluate the core genetic network shaping trichome fate in flowers of an early-divergent angiosperm lineage 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 the canonical trichome gene expression appears to be more conserved in vegetative than in floral tissues across angiosperms.
Assuntos
Proteínas de Arabidopsis , Aristolochia , Aristolochiaceae , Proteínas de Arabidopsis/genética , Aristolochia/genética , Epiderme , Expressão Gênica , Regulação da Expressão Gênica de Plantas , Redes Reguladoras de Genes , Tricomas/genéticaRESUMO
Controlled spatiotemporal cell division and expansion are responsible for floral bilateral symmetry. Genetic studies have pointed to class II TCP genes as major regulators of cell division and floral patterning in model core eudicots. Here we study their evolution in perianth-bearing Piperales and their expression in Aristolochia, a rare occurrence of bilateral perianth outside eudicots and monocots. The evolution of class II TCP genes reveals single-copy CYCLOIDEA-like genes and three paralogs of CINCINNATA (CIN) in early diverging angiosperms. All class II TCP genes have independently duplicated in Aristolochia subgenus Siphisia. Also CIN2 genes duplicated before the diversification of Saruma and Asarum. Sequence analysis shows that CIN1 and CIN3 share motifs with Cyclin proteins and CIN2 genes have lost the miRNA319a binding site. Expression analyses of all paralogs of class II TCP genes in Aristolochia fimbriata point to a role of CYC and CIN genes in maintaining differential perianth expansion during mid- and late flower developmental stages by promoting cell division in the distal and ventral portion of the limb. It is likely that class II TCP genes also contribute to cell division in the leaf, the gynoecium and the ovules in A. fimbriata.