Genome assembly of Ottelia alismoides, a multiple-carbon utilisation aquatic plant

Ottelia Pers. is in the Hydrocharitaceae family. Species in the genus are aquatic, and China is their centre of origin in Asia. Ottelia alismoides (L.) Pers., which is distributed worldwide, is a distinguishing element in China, while other species of this genus are endemic to China. However, O. alismoides is also considered endangered due to habitat loss and pollution in some Asian countries. Ottelia alismoides is the only submerged macrophyte that contains three carbon dioxide-concentrating mechanisms, i.e. bicarbonate (HCO₃^-) use, crassulacean acid metabolism and the C4 pathway. In this study, we present its first genome assembly to help illustrate the various carbon metabolism mechanisms and to enable genetic conservation in the future.

Using DNA and RNA extracted from one O. alismoides leaf, this work produced ∼ 73.4 Gb HiFi reads, ∼ 126.4 Gb whole genome sequencing short reads and ∼ 21.9 Gb RNA-seq reads. The de novo genome assembly was 6,455,939,835 bp in length, with 11,923 scaffolds/contigs and an N50 of 790,733 bp. Genome assembly completeness assessment with Benchmarking Universal Single-Copy Orthologs revealed a score of 94.4%. The repetitive sequence in the assembly was 4,875,817,144 bp (75.5%). A total of 116,176 genes were predicted. The protein sequences were functionally annotated against multiple databases, facilitating comparative genomic analysis.