Long read sequencing of Toona sinensis (A. Juss) Roem: A chromosome-level reference genome for the family Meliaceae.

Chinese mahogany (Toona sinensis) is a woody plant that is widely cultivated in China and Malaysia. Toona sinensis is important economically, including as a nutritious food source, as material for traditional Chinese medicine and as a high-quality hardwood. However, the absence of a reference genome has hindered in-depth molecular and evolutionary studies of this plant. In this study, we report a high-quality T. sinensis genome assembly, with scaffolds anchored to 28 chromosomes and a total assembled length of 596 Mb (contig N50 = 1.5 Mb and scaffold N50 = 21.5 Mb). A total of 34,345 genes were predicted in the genome after homology-based and de novo annotation analyses. Evolutionary analysis showed that the genomes of T. sinensis and Populus trichocarpa diverged ~99.1-103.1 million years ago, and the T. sinensis genome underwent a recent genome-wide duplication event at ~7.8 million years and one more ancient whole genome duplication event at ~71.5 million years. These results provide a high-quality chromosome-level reference genome for T. sinensis and confirm its evolutionary position at the genomic level. Such information will offer genomic resources to study the molecular mechanism of terpenoid biosynthesis and the formation of flavour compounds, which will further facilitate its molecular breeding. As the first chromosome-level genome assembled in the family Meliaceae, it will provide unique insights into the evolution of members of the Meliaceae.

Chemical analysis of a polysaccharide from Cristaria plicata (Leach).

A polysaccharide (MPS) isolated from Cristaria plicata (Leach) consisted of d-glucose. Its structural characteristics were investigated by High Performance Liquid Chromatography (HPLC), infrared analysis, gas chromatography-MS, total acid hydrolysis, methylation analysis, periodate oxidation and Smith degradation. The results indicated that the polysaccharide of C. plicata (Leach) has the weight-average molecular weight of about 2.97 × 106 Da. The structure of the polysaccharide was composed of glucose with α-(1 → 4)-linkages with short exterior chains. The fundamental information obtained from this work is beneficial to the interpretation in the relationship of the polysaccharide structure and its biological functions, and suggests that the polysaccharide from mussel may contribute to be used as a dietary supplement for health foods and therapeutics.