Chromosome numbers in Australian charophytes (Characeae, Charophyceae)

Over the course of a 25 year ecological and taxonomic study, the chromosomes of Australian charophytes (family Characeae) were examined and enumerated. The usual number for members of Chara was n = 14 (for dioecious species) or n = 28 (for monoecious species); although Chara braunii has always been recorded as having n = 14 despite being monoecious. Species in sections Agardhia and Grovesia often had higher ploidy levels [n = 3 x 14 (42), n = 4 x 14 (56)]. The usual number for Australian members of Nitella was n = 9 (for dioecous species) and n = 18, 24 or 27 for monoecious species. Nitella stuartii was an exception, having n = 15 in the specimens studied here. The usual number for monoecious members of Lamprothamnium was n = 28; although, monoecious Lamprothamnium inflatum consistently had n = 14 (populations from Western Australia, Kangaroo Island and South Australia). Chromosome numbers were different for each species of Tolypella examined (n = 11 to 36). There was a high degree of polyploidy within Characeae, and there was evidence that even the lowest numbers of chromosomes represented polyploids (3n for Nitella and 2n for Chara). Polyploidy and consequent doubling or tripling of enzymatic capacity (via potential multiple isozymes) is likely to have a role in the morphological variability and biochemical flexibility of charophytes. Information about the number and appearance of chromosomes (karyotypes) can be used in systematic studies to determine relatedness of taxa and to understand some of the evolutionary processes operating at the population or species level. © 2015 International Phycological Society

NWChem: Past, Present, and Future

0info:eu-repo/semantics/publishe

Reconstruction and phylogenetic significance of a new Equisetum Linnaeus species from the Lower Jurassic of Cerro Bayo (Chubut province, Argentina)

We describe Equisetum dimorphum sp. nov. from the Lower Jurassic of Chubut Province, Patagonia, Argentina. This new species is based on fertile and vegetative remains preserved as impressions of stems, leaves, strobili, transversal sections of the stems showing their anatomy, and terminal pagoda-like structures. The fine-grained sedimentary matrix also preserved detailed impressions of epidermal features. The morphological characters allow a whole-plant reconstruction and assignment to Equisetum. Equisetum dimorphum sp. nov. shows a mosaic of morphological characters that are commonly present in other Mesozoic forms and representatives of the two extant Equisetum subgenera, e.g., sunken stomata and a blunt strobilus apex. Compared to other well-known Mesozoic equisetalean taxa, Equisetum dimorphum sp. nov. appears to be most closely related to a group of Jurassic Equisetum-like plants including Equisetum laterale Phillips and Equisetites ferganensis Seward. Additional evidence for the morphological stasis of the fertile and vegetative organs of extant horsetails is supplied with this new material, adding further support to the hypothesis that the extant horsetails are a successful group that has undergone only little morphological changeover time and that has been present, nearly worldwide, since Jurassic times.VR 2014-5232 The evolutionary history of fern

The <em>Chara</em> Genome: Secondary complexity and implications for plant terrestrialization.

Land plants evolved from charophytic algae, among which Charophyceae possess the most complex body plans. We present the genome of Chara braunii; comparison of the genome to those of land plants identified evolutionary novelties for plant terrestrialization and land plant heritage genes. C.&nbsp;braunii employs unique xylan synthases for cell wall biosynthesis, a phragmoplast (cell separation) mechanism similar to that of land plants, and many phytohormones. C.&nbsp;braunii plastids are controlled via land-plant-like retrograde signaling, and transcriptional regulation is more elaborate than in other algae. The morphological complexity of this organism may result from expanded gene families, with three cases of particular note: genes effecting tolerance to reactive oxygen species (ROS), LysM receptor-like kinases, and transcription factors (TFs). Transcriptomic analysis of sexual reproductive structures reveals intricate control by TFs, activity of the ROS gene network, and the ancestral use of plant-like storage and stress protection proteins in the zygote

The <em>Chara</em> Genome: Secondary complexity and implications for plant terrestrialization.

Land plants evolved from charophytic algae, among which Charophyceae possess the most complex body plans. We present the genome of Chara braunii; comparison of the genome to those of land plants identified evolutionary novelties for plant terrestrialization and land plant heritage genes. C.&nbsp;braunii employs unique xylan synthases for cell wall biosynthesis, a phragmoplast (cell separation) mechanism similar to that of land plants, and many phytohormones. C.&nbsp;braunii plastids are controlled via land-plant-like retrograde signaling, and transcriptional regulation is more elaborate than in other algae. The morphological complexity of this organism may result from expanded gene families, with three cases of particular note: genes effecting tolerance to reactive oxygen species (ROS), LysM receptor-like kinases, and transcription factors (TFs). Transcriptomic analysis of sexual reproductive structures reveals intricate control by TFs, activity of the ROS gene network, and the ancestral use of plant-like storage and stress protection proteins in the zygote