Abstract Detail

Evolutionary Developmental Biology (Evo-Devo)

Lee, Aaron [1], Bhatti, Maryum [1], Rahman-Vyas, Hiba [1], Howarth, Dianella [2], Donoghue, Michael [3], Clement, Wendy [1].

Honeysuckle (Lonicera, Caprifoliaceae, Dipsacales) NAC subfamily Ia evolution and implications for the evolution of organ fusion.

Fusion of plant parts played a key role in generating the diversity of floral form and function across angiosperms. Shifts to fused states may play adaptive roles in pollination, seed dispersal, or in the protection of developing organs (e.g. fruit, seeds). Genes affecting organ fusion include CUP-SHAPED COTYLEDON 1/2 and 3 (CUC1/2 and CUC3), which have been shown to regulate the formation of boundaries of leaves and floral organs in plant model systems. Furthermore, closely related NAC (NAM, ATAF, CUC) transcription factors belonging to NAC subfamily Ia have been shown to affect aspects of cell proliferation. Among the 160 species of honeysuckles (Lonicera, Caprifoliaceae, Dipsacales), there are numerous transitions between unfused and fused organs, such as the fusion of leaves, ovaries, bracts, and bracteoles, thus providing a natural system to study the molecular, developmental, and morphological contexts of fusion from an evolutionary perspective. We applied molecular and computational approaches to isolate and identify orthologs of the six NAC subfamily Ia members described in Arabidopsis thaliana. Broadly sampling across Dipsacales with a focus on Lonicera, we mined novel genome skimming, whole genome, and transcriptome libraries, as well as publicly available genomic and transcriptomic resources. These data were complimented by direct amplification and sequencing of NAC from species for which no genetic resources were available. Phylogenetic analyses revealed six distinct subclades of NAC subfamily Ia in Dipsacales, corresponding with their Arabidopsis orthologs. One putative Dipsacales copy was supported for only three of the six subfamily members: NAC38, NAC58, and NAC46/87. Two Caprifoliaceae-specific copies of CUC1/2 were recovered and three Dipsacales-wide copies of NAC100 were recovered, supporting a more complex history of lineage-specific gene duplications for these orthologs. Notably, a Caprifoliaceae-specific loss of CUC3 was also discovered, further supported by the positive identification of CUC3 orthologs in Adoxaceae, and closely (e.g. Campanulids) and distantly (e.g. Amborella, monocots) related outgroups. Lineage-specific copy number changes of transcription factors directly (CUC1/2 and CUC3) and potentially indirectly (NAC100) regulating organ fusion may result in gene dosage effects, thus impacting the gene regulatory network influencing boundary formation and organ separation. Ultimately, this gene phylogeny provides the first evidence for the molecular basis of the evolution of organ fusion in Lonicera and Caprifoliaceae, and it establishes a robust phylogenetic framework to evaluate NAC gene family evolution in the context of the evolution of organ fusion in Lonicera.

1 - The College of New Jersey, Department of Biology, 2000 Pennington Road, Ewing, NJ, 08628, USA
2 - St. John's University, Department Of Biological Sciences, St. Albert Hall Rm 257, 8000 Utopia Pkwy, Jamiaca, NY, 11439, United States
3 - Yale University, Department Of Ecology And Evolutionary Biology, 21 Sachem Street, Po Box 208106, New Haven, CT, 06511, United States

Keywords:
genome skimming
Lonicera
fusion
CUP-SHAPED COTYLEDON
gene family evolution.

Presentation Type: Oral Paper
Session: EVDV1, Evolutionary Developmental Biology (Evo-Devo)
Location: Virtual/Virtual
Date: Thursday, July 30th, 2020
Time: 10:30 AM
Number: EVDV1003
Abstract ID:341
Candidate for Awards:None