Suchergebnisse

Genome analysis of the pico-eukaryotic marine green alga Prasinoderma coloniale CCMP 1413 unveils the existence of a novel phylum within green plants (Viridiplantae), the Prasinodermophyta, which diverged before the split of Chlorophyta and Streptophyta. Structural features of the genome and gene family comparisons revealed an intermediate position of the P. coloniale genome (25.3 Mb) between the extremely compact, small genomes of picoplanktonic Mamiellophyceae (Chlorophyta) and the larger, more complex genomes of early-diverging streptophyte algae. Reconstruction of the minimal core genome of Viridiplantae allowed identification of an ancestral toolkit of transcription factors and flagellar proteins. Adaptations of P. coloniale to its deep-water, oligotrophic environment involved expansion of light-harvesting proteins, reduction of early light-induced proteins, evolution of a distinct type of C4 photosynthesis and carbon-concentrating mechanism, synthesis of the metal-complexing metabolite picolinic acid, and vitamin B1, B7 and B12 auxotrophy. The P. coloniale genome provides first insights into the dawn of green plant evolution. ; Data availability: Whole-genome assemblies, annotation and raw data for P. coloniale in this study are deposited at the CNGB Nucleotide Sequence Archive92 (CNSA: http://db.cngb. org/cnsa, accession no. CNP0000924). ; The Shenzhen Municipal Government of China and the Guangdong Provincial Key Laboratory of Genome Read and Write. ; http://www.nature.com/natecolevol ; am2021 ; Biochemistry ; Genetics ; Microbiology and Plant Pathology

Mounting evidence suggests that terrestrialization of plants started in streptophyte green algae, favoured by their dual existence in freshwater and subaerial/terrestrial environments. Here, we present the genomes of Mesostigma viride and Chlorokybus atmophyticus, two sister taxa in the earliest-diverging clade of streptophyte algae dwelling in freshwater and subaerial/terrestrial environments, respectively. We provide evidence that the common ancestor of M. viride and C. atmophyticus (and thus of streptophytes) had already developed traits associated with a subaerial/terrestrial environment, such as embryophyte-type photorespiration, canonical plant phytochrome, several phytohormones and transcription factors involved in responses to environmental stresses, and evolution of cellulose synthase and cellulose synthase-like genes characteristic of embryophytes. Both genomes differed markedly in genome size and structure, and in gene family composition, revealing their dynamic nature, presumably in response to adaptations to their contrasting environments. The ancestor of M. viride possibly lost several genomic traits associated with a subaerial/terrestrial environment following transition to a freshwater habitat. ; This work is part of the 10KP project led by BGI-Shenzhen and China National GeneBank. ; We thank G. Günther (http://www.mikroskopia.de/index.html), who took microscopic images of M. viride and C. atmophyticus. Financial support was provided by the Shenzhen Municipal Government of China (grant nos. JCYJ20151015162041454 and JCYJ20160531194327655) and the Guangdong Provincial Key Laboratory of Genome Read and Write (grant no. 2017B030301011). This work is part of the 10KP project led by BGI-Shenzhen and China National GeneBank. ; The Shenzhen Municipal Government of China and the Guangdong Provincial Key Laboratory of Genome Read and Write. ; http://www.nature.com/natureplants ; am2021 ; Biochemistry ; Genetics ; Microbiology and Plant Pathology