Project description:Background and Aims:Comparative floral ontogeny represents a valuable tool to understand angiosperm evolution. Such an approach may elucidate subtle changes in development that discretely modify floral architecture and underlie reproductive lability in groups with superficial homogeneous morphology. This study presents a comparative survey of floral development in Eugenia (Myrtaceae), one of the largest genera of angiosperms, and shows how previously undocumented ontogenetic trends help to explain the evolution of its megadiversity in contrast to its apparent flower uniformity. Methods:Using scanning electron microscopy, selected steps of the floral ontogeny of a model species (Eugenia punicifolia) are described and compared with 20 further species representing all ten major clades in the Eugenia phylogenetic tree. Additional floral trait data are contrasted for correlation analysis and character reconstructions performed against the Myrtaceae phylogenetic tree. Key results:Eugenia flowers show similar organ arrangement patterns: radially symmetrical, (most commonly) tetramerous flowers with variable numbers of stamens and ovules. Despite a similar general organization, heterochrony is evident from size differences between tissues and structures at similar developmental stages. These differences underlie variable levels of investment in protection, subtle modifications to symmetry, herkogamic effects and independent androecium and gynoecium variation, producing a wide spectrum of floral display and contributing to fluctuations in fitness. During Eugenia's bud development, the hypanthium (as defined here) is completely covered by stamen primordia, unusual in other Myrtaceae. This is the likely plesiomorphic state for Myrteae and may have represented a key evolutionary novelty in the tribe. Conclusions:Floral evolution in Eugenia depends on heterochronic patterns rather than changes in complexity to promote flexibility in floral strategies. The successful early establishment of Myrteae, previously mainly linked to the key innovation of fleshy fruit, may also have benefitted from changes in flower structure.
Project description:A new section of Eugenia (Myrtaceae) is described, segregate from Eugenia sect. Phyllocalyx. Phylogenetic studies suggest that Eugenia sect. Phyllocalyx as traditionally delimited is paraphyletic. To maintain the monophyly of each of the sections in Eugenia s.l., we herein opt to circumscribe a new section and recognize six taxa in sect. Speciosae, which has a distribution mostly in southeastern Brazil and northern South America. Nomenclatural notes are made and a taxonomic key is provided for the species of the section.
Project description:miRNAs are small non-coding regulatory RNAs that play important functions in the regulation of gene expression at the post-transcriptional level by targeting mRNAs for degradation or by inhibiting protein translation. Eugenia uniflora is a plant native to tropical America with pharmacological and ecological importance without previous studies about its gene expression and regulation. To date, there is not miRNAs reported in species of Myrtaceae. A small RNA library was constructed to identify miRNAs in Eugenia uniflora. Solexa technology was used to perform high throughput sequencing of the library and the data obtained was analysed using bioinformatics tools. From 14,489,131 clean reads, we obtained 1,852,722 small RNAs representing 45 known miRNA families that have been identified in other plant species. Further analysis using contigs assembled from Illumina mRNA sequencing of leaves from the same individual allowed the prediction of secondary structures of 25 known and 17 novel miRNAs. Potential targets were predicted for the most abundant mature miRNAs in the identified pre-miRNAs based on sequence homology. This study provide the first large scale identification of miRNAs and their potential targets of a species from Myrtaceae without previous genomic sequence resources. Our study provides more information about the evolutionary conservation of the regulatory network of miRNAs in plants and highlights the miRNAs species-specific. mRNA profiles in 1 leaf library of Eugenia uniflora by deep sequencing (Illumina HiSeq2000)