Eleocharis vivipara, an amphibious sedge in the Cyperaceae family, has several remarkable properties, most notably its alternate use of C₃ photosynthesis underwater and C₄ photosynthesis on land. However, the absence of genomic data has hindered its utility for evolutionary and genetic research. Here, we present a high-quality genome for E. vivipara, representing the first chromosome-level genome for the Eleocharis genus, with an approximate size of 965.22 Mb mainly distributed across 10 chromosomes. Its Hi-C pattern, chromosome clustering results, and one-to-one genome synteny across two subgroups indicates a tetraploid structure with chromosome count 2n = 4x = 20. Phylogenetic analysis suggests that E. vivipara diverged from Cyperus esculentus approximately 32.96 million years ago (Mya), and underwent a whole genome duplication (WGD) about 3.5 Mya. Numerous fusion and fission events were identified between the chromosomes of E. vivipara and its close relatives. We demonstrate that E. vivipara has holocentromeres, a chromosomal feature which can maintain the stability of such chromosomal rearrangements. Experimental transplantation and cross-section studies showed its terrestrial culms developed C₄ Kranz anatomy with increased number of chloroplasts in the bundle sheath (BS) cells. Gene expression and weighted gene co-expression network analysis (WGCNA) showed overall elevated expression of core genes associated with C₄ pathway, and significant enrichment of genes related to modified culm anatomy and photosynthesis efficiency. We found evidence of mixed NAD-ME and PCK type C₄ photosynthesis in E. vivipara, and hypothesize that the evolution of C₄ photosynthesis predates the WGD event. The mixed type is dominated by subgenome A and supplemented by subgenome B. Collectively, our findings not only shed light on the evolution of E. vivipara and karyotype within the Cyperaceae family, but also provide valuable insights into the transition between C₃ and C₄ photosynthesis, offering promising avenues for crop improvement and breeding.

Eleocharis vivipara, an amphibious sedge in the Cyperaceae family, has several remarkable properties, most notably its alternate use of C₃ photosynthesis underwater and C₄ photosynthesis on land. However, the absence of genomic data has hindered its utility for evolutionary and genetic research. Here, we present a high-quality genome for E. vivipara, representing the first chromosome-level genome for the Eleocharis genus, with an approximate size of 965.22 Mb mainly distributed across 10 chromosomes. Its Hi-C pattern, chromosome clustering results, and one-to-one genome synteny across two subgroups indicates a tetraploid structure with chromosome count 2n = 4x = 20. Phylogenetic analysis suggests that E. vivipara diverged from Cyperus esculentus approximately 32.96 million years ago (Mya), and underwent a whole genome duplication (WGD) about 3.5 Mya. Numerous fusion and fission events were identified between the chromosomes of E. vivipara and its close relatives. We demonstrate that E. vivipara has holocentromeres, a chromosomal feature which can maintain the stability of such chromosomal rearrangements. Experimental transplantation and cross-section studies showed its terrestrial culms developed C₄ Kranz anatomy with increased number of chloroplasts in the bundle sheath (BS) cells. Gene expression and weighted gene co-expression network analysis (WGCNA) showed overall elevated expression of core genes associated with C₄ pathway, and significant enrichment of genes related to modified culm anatomy and photosynthesis efficiency. We found evidence of mixed NAD-ME and PCK type C₄ photosynthesis in E. vivipara, and hypothesize that the evolution of C₄ photosynthesis predates the WGD event. The mixed type is dominated by subgenome A and supplemented by subgenome B. Collectively, our findings not only shed light on the evolution of E. vivipara and karyotype within the Cyperaceae family, but also provide valuable insights into the transition between C₃ and C₄ photosynthesis, offering promising avenues for crop improvement and breeding.

Eleocharis vivipara, an amphibious plant in Cyperaceae family, was reported to have numerous valuable biological traits, particularly its adaptive photosynthesis plasticity that employing C3 type underwater and C4 type on land. However, the evolutionary and genetic studies of it have been hampered due to lack of genomes. Here we assembled a high-quality genome of E. vivipara, the first chromosome-level genome of Eleocharis genus, with its size ~965.22 Mb and contains 10 chromosomes. Its diagonal Hi-C pattern for adjacent chromosomes, and its 1-to-1 genome synteny relationship for two subgroups suggested it is a tetraploid with n = 2x = 10. Phylogeny result displayed the Eleocharis diverged with Cyperus genus ~23.11 Mya, a closer relationship than others in Cyperaceae. Interestingly, the well 1-to-1 genome synteny result for the subgenome 2 of E. vivipara (x = 5), the genomes of Cyperus esculentus (n = 54) and Rhynchospora tenuis (n = 2), displayed twice chromosomes fusion events resulted to their number reduction from 54 to 5 and then to 2. Compared with its close relative Juncus effusus which has monocentromeres, we found E. vivipara showed characteristics of holocentromeres that can maintain the stability of its fusion chromosomes. Strikingly, transplanting experiment displayed its culms anatomy gradually presented Proto-Kranz structure with increased number of chloroplasts in BS cells in terrestrial culms. Further comparison results not only displayed most of its C4 photosynthesis related genes showed higher expression, but also identified 2,602 up-DEGs that mainly functional in response to water deprivation and ABA, revealed the drought inducted transition of C4 photosynthesis in E. vivipara. Briefly, our results not only shed light on the karyotype evolution of Cyperaceae, but also provided new valuable insights into C3 and C4 transformation that will benefit for crop improvement and breeding.

The epigenetic regulator Dot1, the only known histone H3K79 methyltransferase, has a conserved role in organismal development and homoeostasis. In yeast, Dot1 is required for telomeric silencing and genomic integrity. In Drosophila, Dot1 (Grappa) regulates homoeotic gene expression. Dysregulation of DOT1L (human homologue of Dot1) causes leukaemia and is implicated in dilated cardiomyopathy. In mice, germline disruption of Dot1L and loss of H3K79me2 disrupt vascular and haematopoietic development. Targeted inactivation of Dot1L in principal cells of the mature collecting duct affects terminal differentiation and cell type patterning. However, the role of H3K79 methylation in mammalian tissue development has been questioned, as it is dispensable in the intestinal epithelium, a rapidly proliferating tissue. Here, we used lineage-specific Cre recombinase to delineate the role of Dot1L methyltransferase activity in the mouse metanephric kidney, an organ that develops via interactions between ureteric epithelial (Hoxb7) and mesenchymal (Six2) cell lineages. The results demonstrate that Dot1L^Hoxb7 is dispensable for ureteric bud branching morphogenesis. In contrast, Dot1L^Six2 is critical for the maintenance and differentiation of Six2+ progenitors into epithelial nephrons. Dot1LSix2 mutant kidneys exhibit congenital nephron deficit and cystic dysplastic kidney disease. Molecular analysis implicates defects in key renal developmental regulators, such as Lhx1, Pax2 and Notch. We conclude that the developmental functions of Dot1L-H3K79 methylation in the kidney are lineage-restricted. The link between H3K79me and renal developmental pathways reaffirms the importance of chromatin-based mechanisms in organogenesis.

The epigenetic regulator Dot1, the only known histone H3K79 methyltransferase, has a conserved role in organismal development and homoeostasis. In yeast, Dot1 is required for telomeric silencing and genomic integrity. In Drosophila, Dot1 (Grappa) regulates homoeotic gene expression. Dysregulation of DOT1L (human homologue of Dot1) causes leukaemia and is implicated in dilated cardiomyopathy. In mice, germline disruption of Dot1L and loss of H3K79me2 disrupt vascular and haematopoietic development. Targeted inactivation of Dot1L in principal cells of the mature collecting duct affects terminal differentiation and cell type patterning. However, the role of H3K79 methylation in mammalian tissue development has been questioned, as it is dispensable in the intestinal epithelium, a rapidly proliferating tissue. Here, we used lineage-specific Cre recombinase to delineate the role of Dot1L methyltransferase activity in the mouse metanephric kidney, an organ that develops via interactions between ureteric epithelial (Hoxb7) and mesenchymal (Six2) cell lineages. The results demonstrate that Dot1L^Hoxb7 is dispensable for ureteric bud branching morphogenesis. In contrast, Dot1L^Six2 is critical for the maintenance and differentiation of Six2+ progenitors into epithelial nephrons. Dot1LSix2 mutant kidneys exhibit congenital nephron deficit and cystic dysplastic kidney disease. Molecular analysis implicates defects in key renal developmental regulators, such as Lhx1, Pax2 and Notch. We conclude that the developmental functions of Dot1L-H3K79 methylation in the kidney are lineage-restricted. The link between H3K79me and renal developmental pathways reaffirms the importance of chromatin-based mechanisms in organogenesis.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.