19 research outputs found
The \u3cem\u3eChlamydomonas\u3c/em\u3e Genome Reveals the Evolution of Key Animal and Plant Functions
Chlamydomonas reinhardtii is a unicellular green alga whose lineage diverged from land plants over 1 billion years ago. It is a model system for studying chloroplast-based photosynthesis, as well as the structure, assembly, and function of eukaryotic flagella (cilia), which were inherited from the common ancestor of plants and animals, but lost in land plants. We sequenced the ∼120-megabase nuclear genome of Chlamydomonas and performed comparative phylogenomic analyses, identifying genes encoding uncharacterized proteins that are likely associated with the function and biogenesis of chloroplasts or eukaryotic flagella. Analyses of the Chlamydomonas genome advance our understanding of the ancestral eukaryotic cell, reveal previously unknown genes associated with photosynthetic and flagellar functions, and establish links between ciliopathy and the composition and function of flagella
Enhancement of stress tolerance in transgenic tobacco plants constitutively expressing AtIpk2β, an inositol polyphosphate 6-/3-kinase from Arabidopsis thaliana
Inositol phosphates (IPs) and their turnover products have been implicated to play important roles in stress signaling in eukaryotic cells. In higher plants genes encoding inositol polyphosphate kinases have been identified previously, but their physiological functions have not been fully resolved. Here we expressed Arabidopsis inositol polyphosphate 6-/3-kinase (AtIpk2β) in two heterologous systems, i.e. the yeast Saccharomycescerevisiae and in tobacco (Nicotiana tabacum), and tested the effect on abiotic stress tolerance. Expression of AtIpk2β rescued the salt-, osmotic- and temperature-sensitive growth defects of a yeast mutant strain (arg82Δ) that lacks inositol polyphosphate multikinase activity encoded by the ARG82/IPK2 gene. Transgenic tobacco plants constitutively expressing AtIpk2β under the control of the Cauliflower Mosaic Virus 35S promoter were generated and found to exhibit improved tolerance to diverse abiotic stresses when compared to wild type plants. Expression patterns of various stress responsive genes were enhanced, and the activities of anti-oxidative enzymes were elevated in transgenic plants, suggesting a possible involvement of AtIpk2β in plant stress responses
The Role of bZIP Transcription Factors in Green Plant Evolution: Adaptive Features Emerging from Four Founder Genes
BACKGROUND: Transcription factors of the basic leucine zipper (bZIP) family control important processes in all eukaryotes. In plants, bZIPs are regulators of many central developmental and physiological processes including photomorphogenesis, leaf and seed formation, energy homeostasis, and abiotic and biotic stress responses. Here we performed a comprehensive phylogenetic analysis of bZIP genes from algae, mosses, ferns, gymnosperms and angiosperms. METHODOLOGY/PRINCIPAL FINDINGS: We identified 13 groups of bZIP homologues in angiosperms, three more than known before, that represent 34 Possible Groups of Orthologues (PoGOs). The 34 PoGOs may correspond to the complete set of ancestral angiosperm bZIP genes that participated in the diversification of flowering plants. Homologous genes dedicated to seed-related processes and ABA-mediated stress responses originated in the common ancestor of seed plants, and three groups of homologues emerged in the angiosperm lineage, of which one group plays a role in optimizing the use of energy. CONCLUSIONS/SIGNIFICANCE: Our data suggest that the ancestor of green plants possessed four bZIP genes functionally involved in oxidative stress and unfolded protein responses that are bZIP-mediated processes in all eukaryotes, but also in light-dependent regulations. The four founder genes amplified and diverged significantly, generating traits that benefited the colonization of new environments
Moving inside a MRI room: A risk assessment analysis
International audienc
Pan genome of the phytoplankton Emiliania underpins its global distribution
Coccolithophores have influenced the global climate for over 200
million years1. These marine phytoplankton can account for 20 per
cent of total carbon fixation in some systems2. They form blooms
that can occupy hundreds of thousands of square kilometres and
are distinguished by their elegantly sculpted calcium carbonate exoskeletons
(coccoliths), rendering themvisible fromspace3.Although
coccolithophores export carbon in the form of organic matter and
calcite to the sea floor, they also release CO2 in the calcification
process. Hence, they have a complex influence on the carbon cycle,
driving either CO2 production or uptake, sequestration and export
to the deep ocean4. Here we report the first haptophyte reference
genome, from the coccolithophore Emiliania huxleyi strain
CCMP1516, and sequences from 13 additional isolates. Our analyses
reveal a pan genome (core genes plus genes distributed variably
between strains) probably supported by an atypical complement
of repetitive sequence in the genome. Comparisons across strains
demonstrate thatE. huxleyi, which has long been considered a single
species, harbours extensive genome variability reflected in different
metabolic repertoires. Genome variability within this species
complex seems to underpin its capacity both to thrive in habitats
ranging from the equator to the subarctic and to form large-scale
episodic blooms under a wide variety of environmental conditions