Agrobacterium-mediated gene delivery and transient expression in the red macroalga Chondrus crispus

Molecular resources and transgenic studies in red algae are lagging behind those for green algae. The Agrobacterium-mediated gene-transfer method routinely used in plant transformation has not been fully utilised in the red algae, which, as an important source of phycocolloids, warrant more studies. In this regard, a stepwise methodology was developed for Agrobacterium-mediated transformation of the carrageenophyte Chondrus crispus using pCAMBIA 1301 and a construct featuring a codon-optimized beta-glucuronidase (GUS) reporter gene driven by the endogenous Chondrus actin promoter. The effects of several factors on transformation efficiency were investigated. An intimate association of Chondrus and bacterial cells was observed using scanning electron microscopy. GUS transient expression within Chondrus cortical and medullary cells with both expression cassettes testified to the amenability of Chondrus to Agrobacterium-mediated transformation. Darker staining, indicative of higher GUS activity, was observed with the Chondrus-specific construct, suggesting its superiority over the pCAMBIA 1301. Presence of acetosyringone, the wounding method and the type of co-cultivation medium significantly affected the transformation outcome and efficiency. The Agrobacterium-mediated transient expression presented here constitutes a first step towards tailoring a transformation strategy for Chondrus, which can serve to facilitate further transgenic studies in this important red alga

Data mining approach identifies research priorities and data requirements for resolving the red algal tree of life

<p>Abstract</p> <p>Background</p> <p>The assembly of the tree of life has seen significant progress in recent years but algae and protists have been largely overlooked in this effort. Many groups of algae and protists have ancient roots and it is unclear how much data will be required to resolve their phylogenetic relationships for incorporation in the tree of life. The red algae, a group of primary photosynthetic eukaryotes of more than a billion years old, provide the earliest fossil evidence for eukaryotic multicellularity and sexual reproduction. Despite this evolutionary significance, their phylogenetic relationships are understudied. This study aims to infer a comprehensive red algal tree of life at the family level from a supermatrix containing data mined from GenBank. We aim to locate remaining regions of low support in the topology, evaluate their causes and estimate the amount of data required to resolve them.</p> <p>Results</p> <p>Phylogenetic analysis of a supermatrix of 14 loci and 98 red algal families yielded the most complete red algal tree of life to date. Visualization of statistical support showed the presence of five poorly supported regions. Causes for low support were identified with statistics about the age of the region, data availability and node density, showing that poor support has different origins in different parts of the tree. Parametric simulation experiments yielded optimistic estimates of how much data will be needed to resolve the poorly supported regions (ca. 10³to ca. 10⁴nucleotides for the different regions). Nonparametric simulations gave a markedly more pessimistic image, some regions requiring more than 2.8 10⁵nucleotides or not achieving the desired level of support at all. The discrepancies between parametric and nonparametric simulations are discussed in light of our dataset and known attributes of both approaches.</p> <p>Conclusions</p> <p>Our study takes the red algae one step closer to meaningful inclusion in the tree of life. In addition to the recovery of stable relationships, the recognition of five regions in need of further study is a significant outcome of this work. Based on our analyses of current availability and future requirements of data, we make clear recommendations for forthcoming research.</p

A new monotypic family for the enigmatic crustose red alga Plagiospora gracilis.

Plagiospora gracilis, a mucilaginous crustose red alga growing on subtidal pebbles on both coasts of the North Atlantic Ocean, forms distinctive tetrasporangia (red algal meiotic structures that release haploid tetraspores) but gametophytes have never been reported. In the absence of gametangia, the taxonomic position of this monotypic genus has always been uncertain; it is currently placed provisionally in the Gloiosiphoniaceae (Gigartinales) by comparison with sporophytes of Gloiosiphonia obtained in culture. Dioecious gametophytic crusts of P. gracilis are now reported for the first time, forming gametangia in inconspicuous superficial sori. There is no evidence that fertilization ever occurs in the field although fertile males and female were collected together. In culture, tetraspores grew into tetrasporophytes for three successive generations, by presumed apomictic sporophyte recycling. The life history of P. gracilis may represent a late stage in the loss of sexual reproduction leading to tetraspore-to-tetrasporophyte life histories such as that in Hildenbrandia. Phylogenetic analysis of sequences of the rbcL, LSU (28S) rDNA and coxI (COI-5P) genes for P. gracilis with other Gigartinales resolved P. gracilis as a distinct lineage in a well-supported clade of the families Sphaerococcaceae, Gloiosiphoniaceae, Endocladiaceae, Nizymeniaceae and Phacelocarpaceae. We here propose the monotypic Plagiosporaceae fam. nov. to accommodate P. gracilis

Genetic analysis of the Linnaean Ulva lactuca (Ulvales, Chlorophyta) holotype and related type specimens reveals name misapplications, unexpected origins, and new synonymies.

Current usage of the name Ulva lactuca, the generitype of Ulva, remains uncertain. Genetic analyses were performed on the U. lactuca Linnaean holotype, the U. fasciata epitype, the U. fenestrata holotype, the U. lobata lectotype, and the U. stipitata lectotype. The U. lactuca holotype is nearly identical in rbcL sequence to the U. fasciata epitype, a warm temperate to tropical species, rather than the cold temperate species to which the name U. lactuca has generally been applied. We hypothesize that the holotype specimen of U. lactuca came from the Indo-Pacific rather than northern Europe. Our analyses indicate that U. fasciata and U. lobata are heterotypic synonyms of U. lactuca. Ulva fenestrata is the earliest name for northern hemisphere, cold temperate Atlantic and Pacific species, with U. stipitata a junior synonym. DNA sequences from type specimens provide an unequivocal method for applying names to Ulva species. This article is protected by copyright. All rights reserved

Molecular phylogenies support taxonomic revision of three species of Laurencia (Rhodomelaceae, Rhodophyta), with the description of a new genus

Systematics of the Laurencia complex was investigated using a taxon-rich data set including the chloroplast ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit (rbcL) gene only and a character-rich data set combining the mitochondrial cytochrome oxidase 1 (COI-5P), the rbcL marker, and the nuclear large subunit of the ribosomal operon (LSU). Bayesian and ML analyses of these data sets showed that three species hitherto placed in the genus Laurencia were not closely related to Laurencia sensu stricto. Laurencia caspica was the sister group of the remaining Osmundea species, L. crustiformans joined Palisada and L. flexilis consisted of an independent lineage. In light of these results a new genus, Ohelopapa, was proposed to accommodate L. flexilis. This new genus is morphologically characterized by four pericentral cells in each vegetative axial segment, however it lacks corps en cerise in cortical cells and secondary pit connections between cortical cells which are characteristic in Laurencia. Three novel combinations are proposed to render the classification closer to a natural system: Ohelopapa flexilis, Osmundea caspica, and Palisada crustiformans

Simulation of gait asymmetry and energy transfer efficiency between unilateral and bilateral amputees

Efficient walking or running requires symmetrical gait. Gait symmetry is one of the key factors in efficient human dynamics, kinematics and kinetics. The desire of individuals with a lower-limb amputation to participate in sports has resulted in the development of energy-storing and-returning (ESR) feet. This paper analyses a case study to show the effect of symmetry and asymmetry as well as energy transfer efficiency during periodic jumping between simulated bilateral and unilateral runners. A custom gait analysis system is developed as part of this project to track the motion of the body of a physically active subject during a set of predefined motions. Stance and aerial times are accurately measured using a high speed camera. Gait frequency, the level of symmetry and the non-uniform displacement between left and right foot and their effects on the position of the Centre of Mass (CM) were used as criteria to calculate both peak energies and transformation efficiency. Gait asymmetry and discrepancy of energy transfer efficiency between the intact foot and the ESR are observed. It is concluded that unilateral runners require excessive effort to compensate for lack of symmetry as well as asymmetry in energy transfer, causing fatigue which could be a reason why bilateral amputee runners using ESR feet have a superior advantage over unilateral amputees

Insights into the Evolution of Multicellularity from the Sea Lettuce Genome

We report here the 98.5 Mbp haploid genome (12,924 protein coding genes) of Ulva mutabilis, a ubiquitous and iconic representative of the Ulvophyceae or green seaweeds. Ulva’s rapid and abundant growth makes it a key contributor to coastal biogeochemical cycles; its role in marine sulfur cycles is particularly important because it produces high levels of dimethylsulfoniopropionate (DMSP), the main precursor of volatile dimethyl sulfide (DMS). Rapid growth makes Ulva attractive biomass feedstock but also increasingly a driver of nuisance “green tides.” Ulvophytes are key to understanding the evolution of multicellularity in the green lineage, and Ulva morphogenesis is dependent on bacterial signals, making it an important species with which to study cross-kingdom communication. Our sequenced genome informs these aspects of ulvophyte cell biology, physiology, and ecology. Gene family expansions associated with multicellularity are distinct from those of freshwater algae. Candidate genes, including some that arose following horizontal gene transfer from chromalveolates, are present for the transport and metabolism of DMSP. The Ulva genome offers, therefore, new opportunities to understand coastal and marine ecosystems and the fundamental evolution of the green lineage