Project description:Land plant colonization was a pivotal event in the evolution of photosynthetic eukaryotes. The transition from aquatic to terrestrial environments required complex multisensory systems that enabled plants to perceive and integrate a broader range of environmental cues, such as light intensity and temperature. However, it remains unclear whether this ability was a pre-adaptation or an innovation during early plant terrestrialization. Here, we show that the aquatic streptophyte ancestor of land plants could integrate light and temperature through a complex regulatory network. A conserved regulatory nexus, comprising phytochromes and transcription factors, was active in the last common ancestor of land plants, allowing the first terrestrial colonizers to adapt and flourish on the harsh terrestrial surface of our planet. Thus, we propose that the multisensory integration that enables extant plants to achieve perceptual disambiguation and fine-tune growth in various ecological niches was a pre-adaptation encoded in the genomes of ancestral land plants.
Project description:Land plant colonization was a pivotal event in the evolution of photosynthetic eukaryotes. The transition from aquatic to terrestrial environments required complex multisensory systems that enabled plants to perceive and integrate a broader range of environmental cues, such as light intensity and temperature. However, it remains unclear whether this ability was a pre-adaptation or an innovation during early plant terrestrialization. Here, we show that the aquatic streptophyte ancestor of land plants could integrate light and temperature through a complex regulatory network. A conserved regulatory nexus, comprising phytochromes and transcription factors, was active in the last common ancestor of land plants, allowing the first terrestrial colonizers to adapt and flourish on the harsh terrestrial surface of our planet. Thus, we propose that the multisensory integration that enables extant plants to achieve perceptual disambiguation and fine-tune growth in various ecological niches was a pre-adaptation encoded in the genomes of ancestral land plants.
Project description:The Lemnaceae (duckweeds) are the world’s smallest but fastest growing flowering plants, with a drastically reduced morphology and predominant clonal reproductive habit capable of continuous exponential growth. Here, we present assemblies of 10 Lemna chromosome sets by single molecule nanopore sequencing and chromosome conformation capture. Dynamics of genome evolution in the family are revealed by syntenic comparisons with Wolffia and Spirodela, and diversification of these genera was found to coincide with the “Azolla event”, in which blooms of aquatic macrophytes reduced atmospheric CO2 from greenhouse levels found in the Eocene to those of the current ice age. Orthologous gene comparisons with other aquatic and terrestrial plants uncovered candidate genes for the unique metabolic and developmental features of the family, such as frequent hybrid polyploidy, lack of stomatal closure in high CO2, and accumulation of calcium oxalate, a promising candidate for carbon sequestration. Loss of a spermine-triggered gene network accounts for drastic reduction in stature and preferentially adaxial stomata, a feature of floating aquatic plants. Strikingly, Lemnaceae genomes have selectively lost some of the genes required for RNA interference, including Argonaute genes required for post-zygotic reproductive isolation (the triploid block) and reduced gamete formation. Triploid hybrids arise commonly among Lemna, presumably by hybridization with unreduced gametes, and we have found mutations in highly-conserved ZMM crossover pathway genes that could support polyploid meiosis. Rapid but stable clonal propagation makes Lemna an ideal platform for protein and starch micro-cropping, and for sequestration of dissolved nutrients and atmospheric CO2. Facile regeneration of transgenic fronds from tissue culture, aided by reduced epigenetic silencing, makes Lemna a powerful biotechnological platform, as exemplified by our recent engineering of high-oil Lemna lines that out-perform with oil seed crops.
Project description:The Streptophyta include unicellular and multicellular charophyte green algae and land plants. Colonization of the terrestrial habitat by land plants was a major evolutionary event that has transformed our planet. So far lack of genome information on unicellular charophyte algae hinders our understanding of the origin and the evolution from unicellular to multicellular life in Streptophyta. This work reports the high-quality reference genome and transcriptome of Mesostigma viride, a single-celled charophyte alga with a position at the base of Streptophyta. There are abundant segmental duplications and transposable elements in M. viride, which contribute to a relatively large genome with high gene content compared to other algae and early diverging land plants. This work identifies the origin of genetic tools that multicellular Streptophyta have inherited and key genetic innovations required for evolution of land plants from unicellular aquatic ancestors. The findings shed light on the age-old questions of the evolution of multicellularity and the origin of land plants.
Project description:The Streptophyta include unicellular and multicellular charophyte green algae and land plants. Colonization of the terrestrial habitat by land plants was a major evolutionary event that has transformed our planet. So far lack of genome information on unicellular charophyte algae hinders our understanding of the origin and the evolution from unicellular to multicellular life in Streptophyta. This work reports the high-quality reference genome and transcriptome of Mesostigma viride, a single-celled charophyte alga with a position at the base of Streptophyta. There are abundant segmental duplications and transposable elements in M. viride, which contribute to a relatively large genome with high gene content compared to other algae and early diverging land plants. This work identifies the origin of genetic tools that multicellular Streptophyta have inherited and key genetic innovations required for evolution of land plants from unicellular aquatic ancestors. The findings shed light on the age-old questions of the evolution of multicellularity and the origin of land plants.