RESUMEN
Orchids make up about 10% of all seed plant species, have great economical value, and are of specific scientific interest because of their renowned flowers and ecological adaptations. Here, we report the first draft genome sequence of a lithophytic orchid, Dendrobium catenatum. We predict 28,910 protein-coding genes, and find evidence of a whole genome duplication shared with Phalaenopsis. We observed the expansion of many resistance-related genes, suggesting a powerful immune system responsible for adaptation to a wide range of ecological niches. We also discovered extensive duplication of genes involved in glucomannan synthase activities, likely related to the synthesis of medicinal polysaccharides. Expansion of MADS-box gene clades ANR1, StMADS11, and MIKC(*), involved in the regulation of development and growth, suggests that these expansions are associated with the astonishing diversity of plant architecture in the genus Dendrobium. On the contrary, members of the type I MADS box gene family are missing, which might explain the loss of the endospermous seed. The findings reported here will be important for future studies into polysaccharide synthesis, adaptations to diverse environments and flower architecture of Orchidaceae.
Asunto(s)
Evolución Biológica , Dendrobium/enzimología , Dendrobium/genética , Flores/crecimiento & desarrollo , Genoma de Planta , Glicosiltransferasas/genética , Secuencia de Bases , Vías Biosintéticas , Evolución Molecular , Flores/genética , Genes de Plantas , Glicosiltransferasas/metabolismo , Proteínas de Dominio MADS/genética , Familia de Multigenes , Filogenia , Análisis de Secuencia de ADNRESUMEN
We identified a new holomycotrophic orchid that is related to the myco-heterotrophic Calypsoeae. Because chloroplast genes are primarily lacking or are highly divergent, key morphological characters are either reduced or lost from many myco-heterotrophs, and the phylogenetic relationships of weakly supported paraphyletic Calypsoeae within Epidendroideae have been poorly understood in previous molecular systematic studies. Using chloroplast rbcL, psaB, and matK and nuclear Xdh and ITS sequences, we determined the circumscription and systematic positions of the new orchid and the tribe. The results indicate that the epidendroid taxa include most of the clades that are successively sister to the grade of clades representing previously recognized tribes. Calypsoeae comprising four well-supported clades with 12 genera (except for the previous temporarily placed Wullschlaegelia) is supported as a monophyletic and sister clade to Epidendreae (excluding Coeliinae). The new orchid is nested in Calypsoeae and is a sister to Dactylostalix and/or Calypso. This new holomycotrophic orchid presents a subumbel inflorescence that grows underground, and flower with a long pedicel reputing the ground to open and two fragments at the base of the hook, which are obviously morphologically different from those of Calypsoeae. To accommodate this species in the current generic circumscription, a new genus Yunorchis was created.
Asunto(s)
ADN de Cloroplastos/genética , Genes del Cloroplasto , Orchidaceae/clasificación , Orchidaceae/genética , Plastidios/genética , China , ADN Espaciador Ribosómico/genética , Procesos Heterotróficos/genética , Inflorescencia/anatomía & histología , Inflorescencia/genética , Orchidaceae/anatomía & histología , FilogeniaRESUMEN
Orchidaceae, renowned for its spectacular flowers and other reproductive and ecological adaptations, is one of the most diverse plant families. Here we present the genome sequence of the tropical epiphytic orchid Phalaenopsis equestris, a frequently used parent species for orchid breeding. P. equestris is the first plant with crassulacean acid metabolism (CAM) for which the genome has been sequenced. Our assembled genome contains 29,431 predicted protein-coding genes. We find that contigs likely to be underassembled, owing to heterozygosity, are enriched for genes that might be involved in self-incompatibility pathways. We find evidence for an orchid-specific paleopolyploidy event that preceded the radiation of most orchid clades, and our results suggest that gene duplication might have contributed to the evolution of CAM photosynthesis in P. equestris. Finally, we find expanded and diversified families of MADS-box C/D-class, B-class AP3 and AGL6-class genes, which might contribute to the highly specialized morphology of orchid flowers.
Asunto(s)
Genoma de Planta , Orchidaceae/genética , Evolución Molecular , Perfilación de la Expresión Génica , Regulación del Desarrollo de la Expresión Génica , Regulación de la Expresión Génica de las Plantas , Genes de Plantas , Intrones/genética , Proteínas de Dominio MADS , Tasa de Mutación , Orchidaceae/clasificación , Orchidaceae/metabolismo , Fotosíntesis/genética , Filogenia , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , ARN Mensajero/biosíntesis , ARN Mensajero/genética , ARN de Planta/biosíntesis , ARN de Planta/genética , Alineación de Secuencia , Especificidad de la EspecieRESUMEN
The beauty and complexity of flowers have held the fascination of scientists for centuries, from Linnaeus, to Goethe, to Darwin, through to the present. During the past decade, enormous progress has been made in understanding the molecular regulation of flower morphogenesis. It seems likely that there are both highly conserved aspects to flower development in addition to significant differences in developmental patterning that can contribute to the unique morphologies of different species. Furthermore, floral development is attractive in that several key genes regulating fundamental processes have been identified. Crucial functional studies of floral organ identity genes in diverse taxa are allowing the real insight into the conservation of gene function, while findings on the genetic control of organ elaboration open up new avenues for investigation. These fundamentals of floral organ differentiation and growth are therefore an ideal subject for comparative analyses of flower development, which will lead to a better understanding of molecular mechanisms that control flower morphogenesis.