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Abstract Detail

Green Land: Multiple Perspectives on Green Algal Evolution and the Earliest Land Plants

de Vries, Jan [1].

Comparative functional genomics: inferring the stress response toolkit of the earliest land plants.

Land plants (embryophytes) are a monophyletic clade. The closest relatives of embryophytes are a paraphyletic group of terrestrial and freshwater algae called streptophyte algae. Thus, land plants evolved from streptophyte algae—an evolutionary process that is referred to as plant terrestrialization. During plant terrestrialization, the earliest land plants had to overcome a variety of challenges, including classical terrestrial stressors such as elevated irradiation (photosynthetically active radiation as well as UV), rapid as well as drastic temperature shifts, and drought—challenges that extant land plants face every day. Decades of research into the molecular physiology of land plants have established a detailed understanding of how plants overcome terrestrial stressors—and which genes are required for the molecular stress response of land plants. By comparing the molecular stress response of land plants and streptophyte algae, we can identify which parts of this stress physiological chassis was present in the earliest land plants. To investigate the molecular response that terrestrial stressors elicit in streptophyte algae, I performed comparative functional genomics on one representative of each of the six major classes of streptophyte algae; each species was challenged with cold and high light conditions. The streptophyte algae responded to these stressors by using signaling circuits that are known from land plants for integrating plastid physiology and phytohormone signaling. In my comparative dataset, the representative species for the Zygnematophyceae, Zygnema circumcarinatum, was particularly instructive with regard to the evolution of the phytohormone-mediated signaling that land plants employ during stress. Zygnema expressed a complete set of genes for (potentially) perceiving the stress phytohormone abscisic acid (ABA) and mounting the respective downstream responses. ABA is one of the major stress signaling molecules of land plants and the factors required for its perception and transduction were previously thought to have evolved after plant terrestrialization. I hence further delved into the zygnematophyceaen stress response. Using two representatives of the Zygnematophyceae, I investigated their molecular response to rapid onset of heat stress by applying transcriptomics in tandem with metabolomics. These data again pinpointed the responsiveness of signaling circuits homologous to those of land plants, highlighting a plethora of stress-associated calcium-dependent kinases. In sum, my comparative analyses illuminate the early evolution of key stress response mechanisms that likely played a role during the earliest steps of plants on land—and mediate their response to adverse conditions until today.

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1 - Technische Universitaet Braunschweig, Institute Of Microbiology, Spielmannstr. 7, Braunschweig, 38106, Germany

Genome Evolution
Streptophyte algae
Plant terrestrialization.

Presentation Type: Symposium Presentation
Session: SYM3, Green land: Multiple perspectives on green algal evolution and the earliest land plants
Location: San Luis 1/Starr Pass
Date: Tuesday, July 30th, 2019
Time: 10:45 AM
Number: SYM3007
Abstract ID:318
Candidate for Awards:Margaret Menzel Award

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