Abstract Detail

Development and Structure

Madrigal, Yesenia [1], Alzate, Juan Fernando [2], Pabon Mora, Natalia [3].

Evolution and expression of flowering integrators in neotropical orchids.

During the reproductive transition in Angiosperms, a vegetative apical meristem (SAM) forming leaves, becomes an inflorescence meristem (IM) that forms bracts and flowers. Flowering integrators set the timing and the pace of these reproductive transitions and have been identified in model species like Oryza sativa. Here, the core flowering genetic regulatory network (GRN) relies on early activation of major promoters including Heading date 3a (Hd3a-FLOWERING LOCUS T-FT), Heading date 1 (Hd1-CONSTANS-CO), FLOWERING LOCUS D (OsFD1), and 14–3–3 proteins, which form a florigen activation complex to regulate the reproductive transition. This is followed by the transcription of OsMADS22-47 (AGAMOUS-like 24/ SHORT VEGETATIVE PHASE-AGL24/SVP) and OsMADS50-51 (SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1-SOC1) that activate floral meristem identity genes like OsMADS14-15 (FRUITFUL-like-FUL). Other genes like TERMINAL FLOWER LOCUS 1 (TFL1) and OsMADS55 (AGL24/SVP) repress flowering to control the vegetative phase's maintenance. On the other hand, in model grasses like wheat, there are two major repressors like FLOWERING LOCUS C (FLC) and VERNALIZATION 2 (VRN2) to extend vegetative phases in vernalized species. We evaluated the flowering GRN in the Orchidaceae, to identify major flowering integrators in a megadiverse family with taxa able to colonize transitional habitats. We first sequenced 13 reference transcriptomes of neotropical orchid species representing different phylogenetic positions, habitats, and floral forms. We isolated homologs and performed phylogenetic analyses of all genes from the flowering GRN in order to understand the evolution of these gene lineages. Our ML results indicate that FT/TFL1, FD, AGL24/SVP, SOC1, and FUL gene lineages have been subject to multiple duplications in monocots, and additional duplications in Orchidaceae. In turn, orchids have a higher copy number of all genes when compared to the model O. sativa. Conversely, flowering repressors like TFL1 are found in lower copy number and FLC genes are lost in Orchidaceae, suggesting major changes in the negative control of flowering. Finally, to identify the full set of flowering integrators in a single species, we performed large-scale transcriptome analyses from the SAM and the IM in Epidendrum fimbriatum, a miniature terrestrial orchid with constant flowering in the field. Our results from the differentially expressed genes point to a modified set of flowering integrators in the reproductive transitions of orchid species. Altogether, our data suggest that the flowering GRN in orchids has significant variations in copy number and expression patterns when compared to the canonical rice flowering GRN.

1 - Universidad de Antioquia, Ciudad universitaria, Biologia, Medellin, ANT, 050010, Colombia
2 - Universidad de Antioquia, Centro Nacional de Secuenciación Genómica, Medellin, ANT, Colombia
3 - Universidad de Antioquia, Biologia, Medellin, ANT, 050010, Colombia

Keywords:
gene regulatory network
Orchidaceae
Flowering
Meristem development
differential gene expression
Gene evolution
evo-devo
flowering plant evolution.

Presentation Type: Oral Paper
Session: DS1, Development and Structure I
Location: /
Date: Tuesday, July 20th, 2021
Time: 10:30 AM(EDT)
Number: DS1003
Abstract ID:451
Candidate for Awards:Katherine Esau Award