Abstract Detail

Pteridology

Rodríguez, Carolina [1], Vasco, Alejandra [2], Ambrose, Barbara [3], Pabon Mora, Natalia [1].

Understanding the contribution of LFY and PEBP flowering genes to fern leaf dimorphism.

Ferns can exhibit one of the three states of leaf dimorphism gradient when mature: Monomorphic (no differentiation between fertile and sterile leaves), Hemidimorphic (portion of a fertile leaf differentiated), and Holomorphic (morphologically distinct fertile and sterile leaves). In angiosperms dimorphism is a fixed character resulting in the stamens and carpels, which are modified leaves key in their reproductive success. The genetic mechanisms controlling reproductive transition in flowering plants are well known, but changes triggering reproduction in ferns have been less studied. Currently, it is not clear how ferns promote transition to reproduction and sporogenesis, and how that relates to the morphological changes in leaves. Taking as reference the angiosperm reproductive transition genes, two candidate transcription factors are proposed as “reproductive genes” in ferns: the PEBP (Phosphatidyl Ethanolamine Binding Proteins) family which comprises TERMINAL FLOWER1-Like (TFL1-Like), FLOWERING LOCUS T-Like (FT-Like), and MOTHER OF FT AND TFL1-Like (MFT-Like) genes. These genes integrate environmental factors and have been reported as both activators and repressors in flowering transition. The second proposed gene is LEAFY (LFY), which is responsible for floral meristem identity and thus, floral structures. Both genes are present in seedless vascular plants, but the number of copies, sequence variation, expression, and function in ferns with different leaf dimorphism remains unknown. We have isolated PEBPhomologs in land plants targeting ferns and lycophytes from public repositories and our own generated transcriptomes from selected ferns for each dimorphic state. Maximum Likelihood (ML) analyses were performed and our preliminary results show that PEBP genes have undergone three main duplication events where: (1) FT/TFL1 genes are seed-plant specific, (2) ferns have “Fern FT/TFL1 genes” an additional clade of PEBP genes that predates FT/TFL1 duplication, and (3) lycophytes and ferns have MFT orthologs with an additional duplication in ferns. For LFY, as previously reported, we found that: (1) LFY genes are present in viridiplantae, (2) The NDLY paraloguegene is specific to gymnosperms, and (3) contrary to what has been reported, multiple species-specific duplications have occurred across ferns. Finally, using comparative anatomy we have identified key developmental stages in the ferns Adiantum capillus-veneris (monomorphic), Anemia villosa (hemidimorphic), Equisetum bogotense (holodimorphic), and Equisetum giganteum (holodimorphic). We are in the process of evaluating expression patterns of PEBP and LFY genes in these fern species and one lycophyte, to assess their putative contribution to the transition to reproduction and the shifts in leaf morphology.

1 - Universidad de Antioquia, Instituto de Biología, Medellín, Colombia
2 - Botanical Research Institute Of Texas, 1700 University Drive, Fort Worth, TX, 76107, United States
3 - The New York Botanical Garden, 2900 Southern Blvd, Bronx, NY, 10458, United States

Keywords:
Leaf evolution
Dimorphism
Gene evolution
PEBP
LEAFY
ferns
Lycophytes
Reproductive transition
Evo-Devo.

Presentation Type: Oral Paper
Session: PTER1, Pteridology I
Location: San Pedro 1/Starr Pass
Date: Monday, July 29th, 2019
Time: 10:30 AM
Number: PTER1010
Abstract ID:758
Candidate for Awards:None