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Najas (Hydrocharitaceae), a cosmopolitan genus of about 40 species, stands among the most intricately adapted of aquatic angiosperms. All species are dioecious or monoecious and are entirely submersed and pollinated underwater (a form of hydrophily). Unlike most Hydrocharitaceae, Najas species are annuals that rely primarily on seed for reproduction. Most of their anatomical and morphological features are characterized by extreme reduction. Submersed plants like Najas face unique physiological challenges as they grow across a broad ecological gradient ranging from shallow, warm, and bright waters to deep, dark, and cold waters. How these plants maintain essential metabolic processes under such diverse conditions has not yet been explained in any detail. We are beginning to investigate this question by comparing sequence data obtained from complete chloroplast genomes of Najas and related taxa. Already this work has provided evidence of unique alterations of the chloroplast psaA/psaB operon and the loss/pseudogenization of photosynthetic genes that otherwise are conserved strongly across terrestrial plants. In addition to reviewing the adaptive implications of these features, we report new evidence to demonstrate that plastid coding regions of Najas species diverged by positive selection with respect to those of other Hydrocharitaceae, monocotyledons, and angiosperms. Ultimately, the objective of this work is to identify key regions of the chloroplast and nuclear genomes that have facilitated the major ecological transition of flowering plant species from life on land to life in the water.Click the "Page Previews" tab for a list of other paper titles available.
Ursula M. King Ursula M. King's Author Page
Donald ("Don") H. Les is a plant systematist who studies aquatic angiosperm evolution using molecular approaches. He attended Eastern Michigan University (B.S. and M.S. degrees) from 1972-1980 and received a Ph.D. at The Ohio State University in 1986. His non-academic appointments included positions with The Nature Conservancy, U.S. Fish & Wildlife Service, and Lee Co. (Florida) Hyacinth Control District. He was an Assistant and Associate Professor at the University of Wisconsin-Milwaukee from 1986-1992. In 1992 Don accepted an Associate Professorship at the Uni versity of Connecticut where he currently serves as a Full Professor. He was a Fulbright senior scholar during 1999-2000, which enabled him to study aquatic flowering plants in Australia. In addition to his many contributions on aquatic monocotyledons, he also has authored a book on the Aquatic Dicotyledons of North America (2017). Donald H. Les's Author Page
Elena L Peredo is a Research Associate at the Marine Biological Laboratory. Her research is focused on adaptations associated with shifts between terrestrial and aquatic lifestyles during plant evolution, focusing on the genetic basis of physiological traits that evolve under radically different environmental conditions upon colonization of new ecosystems. Because internal and external microbial comunities are invariably intertwined with plants in natural environments, she is also interested in the broader consequences of the movements of plants and their associated microbiomes between habitats, whether transitions between emerged and submerged environments, or introductions of non-native plants to new locations. Elena L. Peredo's Author Page
Lori K. Benoit Lori K. Benoit's Author Page