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Abstract Detail



Frontiers in fern gametophyte research

Greer, Gary K. [1].

A Working Model of Phytohormonal Control of Leptosporangiate Fern Gametophyte Development.

Numerous lines of inquiry (fossil, physiologic, genetic, and computer simulation) are necessary to deduce the evolution and diversification of the controls of development of land plants. Elucidating the evolution of gametophytes is perhaps most challenging due to their poor fossil record. However, comparative genetic and physiological studies of extant taxa can reveal commonalities that are most likely ancestral and differences that are responsible for diversification in form, niche, and solution to reproductive challenges. Past research regarding the morphology and physio-genetic controls of form and reproduction in fern gametophytes has not yielded a cohesive model due to a limited number of studies as compared to seed plants. I offer a simplistic working model of the evolution of phytohormonal controls of leptosporangiate fern gametophyte development, including the evolution of the gender-influencing pheromone antheridiogen, as a framework for future research. The model is an overlay of current phytohormonal models for seed plant shoot apices onto a stereotypical cordate gametophyte and emphasizes the actions of cytokinin, auxin, and gibberellin. Although consistent with previously published studies of fern gametophytes, suggesting that some core physiological controls shared with seed plant sporophytes reflect an “ancestral toolbox”, many aspects of the model are necessarily basic and untested. Results from recent comparative studies between Osmundales and core-leptosporangiate species support the hypothesis that antheridiogen systems evolved from an ancestral condition distinguished by: (1) a default antheridium-to-archegonium sequence of gametangial production following the prerequisite formation of an apical, multicellular, notch-meristem and (2) a putative antheridiogen system in which precordate, asexual-cordate, and male-cordate stages were prolonged by exogenous, conspecific gibberellins that are endogenously associated with the formation of a pluricellular notch-meristem. According to this model, evolution of a fully-formed antheridiogen system required uncoupling of the linkage between meristem development (i.e., notch-formation) and production of antheridia. The proposed model provides an initial framework for targeting bioassays and omic-based studies to elucidate the evolution of leptosporangiate fern gametophytes, as well providing a basis for comparison with their sporophyte counterparts.

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1 - Grand Valley State University, Biology, 1 Campus Drive, Allendale, MI, 49401-1000, USA

Keywords:
fern
gametophyte
Development
Working Model
Phytohormones
Gender expression
Meristem.

Presentation Type: Symposium or Colloquium Presentation
Session: C4
Location: Prince of Wales/Riverside Hilton
Date: Tuesday, July 30th, 2013
Time: 11:00 AM
Number: C4010
Abstract ID:430
Candidate for Awards:None


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