Project description:Genome sequencing of UK duckweed panel including Lemna minor, Lemna japonica, Lemna minuta, Lemna turionifera and Spirodela polyrhiza accessions.
Project description:Duckweeds are a monophyletic group of rapidly reproducing aquatic monocots in the Lemnaceae family. Spirodela polyrhiza, the Greater Duckweed, has the largest body plan yet the smallest genome size in the family (1C = 150 Mb). Given their clonal, exponentially fast reproduction, a key question is whether genome structure is conserved across the species in the absence of meiotic recombination. We generated a highly contiguous, chromosome-scale assembly of Spirodela polyrhiza line Sp7498 using Oxford Nanopore plus Hi-C scaffolding (Sp7498_HiC) that is highly syntenic with a related line (Sp9509). Both the Sp7498_HiC and Sp9509 genome assemblies reveal large chromosomal misorientations in a recent PacBio assembly of Sp7498, highlighting the necessity of orthogonal long-range scaffolding techniques like Hi-C and BioNano optical mapping. Proteome analysis of Sp7498 verified the expression of nearly 2,250 proteins and revealed a high level of proteins involved in photosynthesis and carbohydrate metabolism among other functions. In addition, a strong increase in chloroplast proteins was observed that correlated to chloroplast density. This Sp7498_HiC genome was generated cheaply and quickly with a single Oxford Nanopore MinION flow cell and one Hi-C library in a classroom setting. Combining these data with a mass spectrometry-generated proteome, demonstrates that duckweed is a model for genomics- and proteomics-based education.
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 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 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 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 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.