Abstract Detail

Characteristics of nectar, nectaries, and nectar spurs

Krosnick, Shawn [1], Maynord, Silas [2], Hearn, David [3], Hawkins, Angela [4], Shrestha, Bikash [5].

Nectaromania in Passifloraceae: summarizing our current understanding of extrafloral nectaries in a morphologically challenging lineage.

In 1978, Jacob Lorch coined the term "nectaromania" to describe the fascination botanists had with floral nectaries that began around 1825. Countless scientists, including Linnaeus, de Candolle, and Darwin debated the nature of these structures, producing seminal anatomical and morphological studies that created the foundation for our understanding of nectaries today. Lorch then foretold of a new surge in interest yet to come, this time directed at extrafloral nectaries. Indeed his prediction has largely come true, especially in the last 20 years. Our understanding of the ecology, phylogenetic distribution, physiology, and genetic regulation of extrafloral nectaries (EFNs) has increased exponentially. With the advent of transcriptome sequencing, identification of genes implicated in EFN form and function is now possible, allowing for a much deeper understanding these structures. With the most diverse leaf morphology of any group of angiosperms, we have used the Passifloraceae as a model system in which to examine the nature of EFNs at multiple levels. This talk will present a summary of the status of this research, including morphological, anatomical, developmental, and genetic data. Comparative transcriptomic analyses of EFNs in Adenia and Passiflora have resulted in the identification of multiple candidate genes with potential roles in EFN morphogenesis. The increased expression of a subset of these genes (SHI RELATED SEQUENCE 1-like, NGATHA-like containing domain #1 and #2, and NAC domain-containing protein 8) during development of EFNs in Passiflora has been confirmed via qPCR with fresh tissue. Moreover, increased expression of these genes is consistent in phylogenetically and morphologically diverse species not part of the original transcriptome study. EFNs in Passiflora also share similar expression patterns with leaf teeth, raising even deeper phylogenetic questions about their origins. Close relatives in the Salicaceae (e.g. Populus) may secrete resinous and/or sugar-rich exudates from leaf teeth or EFNs, in some cases secreted via hydathodes. Considering the known functional roles of candidate genes expressed in Passiflora EFNs brings exciting new insights into the true nature of these structures. For example, NGATHA and NAC are expressed in both leaf hydathodes and leaf teeth in Arabidopsis; this may represent be a link between these seemingly unrelated structures in Passiflora. Yet, caveats exist: while homology is often considered in reference to organs or tissues, gene expression manifests at a cellular level. This emphasizes the importance of careful anatomical and developmental work to complement these powerful genetic approaches. 

1 - Tennessee Tech University, Dept. Of Biology, 1100 East Dixie Avenue, Pennebaker Hall #207, Cookeville, TN, 38505, United States
2 - 324 Woodland Street, Livingston, TN, 38570, United States
3 - Towson University, Biology, 8000 York Road, Towson, MD, 21252, United States
4 - Texas A&M University, Department Of Biology, 3258 TAMU, College Station, TX, 77843, United States
5 - The University of Texas at Austin, Department of Integrative Biology , 2415 Speedway #C0930, Austin, TX, 78712, USA

leef teeth.

Presentation Type: Colloquium Presentations
Session: COL02, Characteristics of nectar, nectaries and nectar spurs
Location: Virtual/Virtual
Date: Monday, July 27th, 2020
Time: 12:30 PM
Number: COL02009
Abstract ID:586
Candidate for Awards:None

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