Labellum transcriptome reveals alkene biosynthetic genes involved in orchid sexual deception and pollination-induced senescence

Abstract

One of the most remarkable pollination strategy in orchids biology is pollination by sexual deception, in which the modified petal labellum lures pollinators by mimicking the chemical (e.g. sex pheromones), visual (e.g. colour and shape/size) and tactile (e.g. labellum trichomes) cues of the receptive female insect species. The present study aimed to characterize the transcriptional changes occurring after pollination in the labellum of a sexually deceptive orchid (Ophrys fusca Link) in order to identify genes involved on signals responsible for pollinator attraction, the major goal of floral tissues. Novel information on alterations in the orchid petal labellum gene expression occurring after pollination demonstrates a reduction in the expression of alkene biosynthetic genes using O. fusca Link as the species under study. Petal labellum transcriptional analysis revealed downregulation of transcripts involved in both pigment machinery and scent compounds, acting as visual and olfactory cues, respectively, important in sexual mimicry. Regulation of petal labellum senescence was revealed by transcripts related to macromolecules breakdown, protein synthesis and remobilization of nutrients.

Tissue-Specific Floral Transcriptome Analysis of the Sexually Deceptive Orchid Chiloglottis trapeziformis Provides Insights into the Biosynthesis and Regulation of Its Unique UV-B Dependent Floral Volatile, Chiloglottone 1

“…A total of 82,564 (37.2%) of 221,668 contigs in the final assembly were successfully ascribed with GO, InterPro, and/or MapMan BIN categories (Supplementary Figures 3A,B). Many GO assignments were comparable to other floral transcriptomes of orchids (Monteiro et al, 2012; Sedeek et al, 2013). Additional MapMan BIN mappings provide a complimentary annotation scheme to GO.…”

Transcriptome and Proteome Data Reveal Candidate Genes for Pollinator Attraction in Sexually Deceptive Orchids

“…Differential expression and/or activity of different orchid SADs is responsible for alkene double-bond differences among O. sphegodes and O. exaltata [20], [24]. Homologous to seven known Arabidopsis SAD genes [61], we identified 13 different SAD transcripts in 7 gene models (isogroups) from transcriptome assembly that likely correspond to 6 known Ophrys SAD genes [20], [24], [33]. This suggests that our knowledge of the identity of Ophrys SAD genes is relatively complete.…”

“…Currently, there is no genome sequence publically available for any orchid, and there are no comprehensive genome, transcriptome, or proteome resources for sexually deceptive orchids. A small number of orchid expressed sequence tags (ESTs) obtained by Sanger sequencing are available [29], [30], [31], [32], including 277 ESTs from Ophrys [33]. Although transcriptomes of the Phalaenopsis and Oncidium ‘Gower Ramsey’ orchids have recently been released [34], [35], these orchids are from the subfamily Epidendroideae and are only distantly related to Ophrys (subfamily Orchidoideae).…”

Marked hybridization and introgression in Ophrys sect. Pseudophrys in the western Iberian Peninsula

“…across its range and it is possible to recognize different regional pollinators. No pollinator data for the region studied here are available; except that a male A. livens was found trapped in the textile material that prevented pollination of this species in the field in a genomic experiment (Monteiro, 2011; Monteiro et al, 2012). In the absence of such data for the region studied here and assuming that these would be highly specific and thought to act as isolating factors (Paulus and Gack, 1990a; Schiestl, and Ayasse, 2002), we would expect to find well‐delimited species.…”