Origens moleculares dos frutos de angiospermas

Abstract

Angiosperms are the only plants that produce fruits surrounding its seeds, protecting them and attracting dispersers, which permitted the groups’ rapid diversification and the coevolution with some animal species. Despite having well-described ontogenetic origins (coming from the ovary), the understanding about the origin and evolution of fruits is still limited. Fleshy structures associated with dispersion and seed protection are also present in gymnosperms, coming from the seed’s tegument, modified bracts or aril. Its resemblance to fruits defies our understanding of its evolution. Comparative studies indicate a partial homology between the angiosperm’s molecular machinery of fruit development and gymnosperm’s “fruits”, dating back to the common ancestor of seed plants (Spermatophyta), while others point to a case of convergent evolution. In this study, we conducted a differential gene expression analysis throughout the development of fruits in different angiosperm lineages in order to identify conserved gene sets. We found 6.542 groups of ortholog genes (orthogroups) with differentially expressed members through the fruit’s development in most of the analyzed species, being 2.789 shared between all of them. We also looked for orthologs to these genes between those used by gymnosperms to develop its fleshy structures. We obtained 762 orthogroups shared between Ginkgo biloba and most of the angiosperm species, being 450 of these shared between all of them. Were found conserved between angiosperms and shared with gymnosperms glycosyl hydrolases (GHs), transcription factors (TFs) and transcriptional regulators related to the degradation of pectins (GH28) and xylan (GH10) and to the signal transduction of cytokinin, auxin, gibberellin, ethylene and abscisic acid (B3-ARF, AUX/IAA and APETALA2). GHs were identified related to the fruit’s sugar composition and softening (GH27, GH13, GH36, GH100 and GH14), along with TFs related to its format (OFP). Our results indicate a partial genetic homology between angiosperm fruits and fruit-like structures in gymnosperms, as well as gene sets specifically related to the fruit’s development in angiosperms, which may explain synapomorphic characteristics in flowering plants.