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Genome sequence of the agarwood tree Aquilaria sinensis (Lour.) Spreng: the first chromosome-level draft genome in the Thymelaeceae family.

ABSTRACT: BACKGROUD:Aquilaria sinensis (Lour.) Spreng is one of the important plant resources involved in the production of agarwood in China. The agarwood resin collected from wounded Aquilaria trees has been used in Asia for aromatic or medicinal purposes from ancient times, although the mechanism underlying the formation of agarwood still remains poorly understood owing to a lack of accurate and high-quality genetic information. FINDINGS:We report the genomic architecture of A. sinensis by using an integrated strategy combining Nanopore, Illumina, and Hi-C sequencing. The final genome was ?726.5 Mb in size, which reached a high level of continuity and a contig N50 of 1.1 Mb. We combined Hi-C data with the genome assembly to generate chromosome-level scaffolds. Eight super-scaffolds corresponding to the 8 chromosomes were assembled to a final size of 716.6 Mb, with a scaffold N50 of 88.78 Mb using 1,862 contigs. BUSCO evaluation reveals that the genome completeness reached 95.27%. The repeat sequences accounted for 59.13%, and 29,203 protein-coding genes were annotated in the genome. According to phylogenetic analysis using single-copy orthologous genes, we found that A. sinensis is closely related to Gossypium hirsutum and Theobroma cacao from the Malvales order, and A. sinensis diverged from their common ancestor ?53.18-84.37 million years ago. CONCLUSIONS:Here, we present the first chromosome-level genome assembly and gene annotation of A. sinensis. This study should contribute to valuable genetic resources for further research on the agarwood formation mechanism, genome-assisted improvement, and conservation biology of Aquilaria species.

SUBMITTER: Ding X

PROVIDER: S-EPMC7050300 | biostudies-literature | 2020 Mar

REPOSITORIES: biostudies-literature

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Genome sequence of the agarwood tree Aquilaria sinensis (Lour.) Spreng: the first chromosome-level draft genome in the Thymelaeceae family.

Ding Xupo X Mei Wenli W Lin Qiang Q Wang Hao H Wang Jun J Peng Shiqing S Li Huiliang H Zhu Jiahong J Li Wei W Wang Pei P Chen Huiqin H Dong Wenhua W Guo Dong D Cai Caihong C Huang Shengzhuo S Cui Peng P Dai Haofu H

GigaScience 20200301 3

<h4>Backgroud</h4>Aquilaria sinensis (Lour.) Spreng is one of the important plant resources involved in the production of agarwood in China. The agarwood resin collected from wounded Aquilaria trees has been used in Asia for aromatic or medicinal purposes from ancient times, although the mechanism underlying the formation of agarwood still remains poorly understood owing to a lack of accurate and high-quality genetic information.<h4>Findings</h4>We report the genomic architecture of A. sinensis ...[more]

PMID: 32118265

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Project description:Recently, some new Qi-Nan clones of Aquilaria sinensis (Lour.) Spreng which intensively produces high-quality agarwood have been identified and propagated through grafting techniques. Previous studies have primarily focused on ordinary A. sinensis and the differences in composition when compared to Qi-Nan and ordinary A. sinensis. There are few studies on the formation mechanism of Qi-Nan agarwood and the dynamic changes in components and endophytic fungi during the induction process. In this paper, the characteristics, chemical composition, and changes in endophytic fungi of Qi-Nan agarwood induced after 1 year, 2 years, and 3 years were studied, and Qi-Nan white wood was used as the control. The results showed that the yield of Qi-Nan agarwood continued to increase with the induction time over a period of 3 years, while the content of alcohol extract from Qi-Nan agarwood reached its peak at two years. During the formation of agarwood, starch and soluble sugars in xylem rays and interxylary phloem are consumed and reduced. Most of the oily substances in agarwood were filled in xylem ray cells and interxylary phloem, and a small amount was filled in xylem vessels. The main components of Qi-Nan agarwood are also chromones and sesquiterpenes. With an increasing induction time, the content of sesquiterpenes increased, while the content of chromones decreased. The most abundant chromones in Qi-Nan agarwood were 2-(2-Phenethyl) chromone, 2-[2-(3-Methoxy-4-hydroxyphenyl) ethyl] chromone, and2-[2-(4-Methoxyphenyl) ethyl] chromone. Significant differences were observed in the species of the endophytic fungi found in Qi-Nan agarwood at different induction times. A total of 4 phyla, 73 orders, and 448 genera were found in Qi-Nan agarwood dominated by Ascomycota and Basidiomycota. Different induction times had a significant effect on the diversity of the endophytic fungal community in Qi-Nan. After the induction of agarwood formation, the diversity of Qi-Nan endophytic fungi decreased. Correlation analysis showed that there was a significant positive correlation between endophytic fungi and the yield, alcohol extract content, sesquiterpene content, and chromone content of Qi-Nan agarwood, which indicated that endophytic fungi play a role in promoting the formation of Qi-Nan agarwood. Qi-Nan agarwood produced at different induction times exhibited strong antioxidant capacity. DPPH free radical scavenging activity and reactive oxygen species clearance activity were significantly positively correlated with the content of sesquiterpenes and chromones in Qi-Nan agarwood.

Project description:Aquilaria sinensis (Lour.) Gilg is an important medicinal woody plant producing agarwood, which is widely used in traditional Chinese medicine. High-throughput sequencing of chloroplast (cp) genomes enhanced the understanding about evolutionary relationships within plant families. In this study, we determined the complete cp genome sequences for A. sinensis. The size of the A. sinensis cp genome was 159,565 bp. This genome included a large single-copy region of 87,482 bp, a small single-copy region of 19,857 bp, and a pair of inverted repeats (IRa and IRb) of 26,113 bp each. The GC content of the genome was 37.11%. The A. sinensis cp genome encoded 113 functional genes, including 82 protein-coding genes, 27 tRNA genes, and 4 rRNA genes. Seven genes were duplicated in the protein-coding genes, whereas 11 genes were duplicated in the RNA genes. A total of 45 polymorphic simple-sequence repeat loci and 60 pairs of large repeats were identified. Most simple-sequence repeats were located in the noncoding sections of the large single-copy/small single-copy region and exhibited high A/T content. Moreover, 33 pairs of large repeat sequences were located in the protein-coding genes, whereas 27 pairs were located in the intergenic regions. Aquilaria sinensis cp genome bias ended with A/T on the basis of codon usage. The distribution of codon usage in A. sinensis cp genome was most similar to that in the Gonystylus bancanus cp genome. Comparative results of 82 protein-coding genes from 29 species of cp genomes demonstrated that A. sinensis was a sister species to G. bancanus within the Malvales order. Aquilaria sinensis cp genome presented the highest sequence similarity of >90% with the G. bancanus cp genome by using CGView Comparison Tool. This finding strongly supports the placement of A. sinensis as a sister to G. bancanus within the Malvales order. The complete A. sinensis cp genome information will be highly beneficial for further studies on this traditional medicinal plant. Moreover, the results will enhance our understanding about the evolution of cp genomes of the Malvales order, particularly with regard to the role of A. sinensis in plant systematics and evolution.

Project description:BackgroundAgarwood is a traditional Chinese medicine used as a clinical sedative, carminative, and antiemetic drug. Agarwood is formed in Aquilaria sinensis when A. sinensis trees are threatened by external physical, chemical injury or endophytic fungal irritation. However, the mechanism of agarwood formation via chemical induction remains unclear. In this study, we characterized the transcriptome of different parts of a chemically induced A. sinensis trunk sample with agarwood. The Illumina sequencing platform was used to identify the genes involved in agarwood formation.Methodology/principal findingsA five-year-old Aquilaria sinensis treated by formic acid was selected. The white wood part (B1 sample), the transition part between agarwood and white wood (W2 sample), the agarwood part (J3 sample), and the rotten wood part (F5 sample) were collected for transcriptome sequencing. Accordingly, 54,685,634 clean reads, which were assembled into 83,467 unigenes, were obtained with a Q20 value of 97.5%. A total of 50,565 unigenes were annotated using the Nr, Nt, SWISS-PROT, KEGG, COG, and GO databases. In particular, 171,331,352 unigenes were annotated by various pathways, including the sesquiterpenoid (ko00909) and plant-pathogen interaction (ko03040) pathways. These pathways were related to sesquiterpenoid biosynthesis and defensive responses to chemical stimulation.Conclusions/significanceThe transcriptome data of the different parts of the chemically induced A. sinensis trunk provide a rich source of materials for discovering and identifying the genes involved in sesquiterpenoid production and in defensive responses to chemical stimulation. This study is the first to use de novo sequencing and transcriptome assembly for different parts of chemically induced A. sinensis. Results demonstrate that the sesquiterpenoid biosynthesis pathway and WRKY transcription factor play important roles in agarwood formation via chemical induction. The comparative analysis of the transcriptome data of agarwood and A. sinensis lays the foundation for elucidating the mechanism of agarwood formation via chemical induction, and thus, enables future improvements in agarwood quality while protecting endangered wild A. sinensis.

Dataset Information

Genome sequence of the agarwood tree Aquilaria sinensis (Lour.) Spreng: the first chromosome-level draft genome in the Thymelaeceae family.

Publications

Genome sequence of the agarwood tree Aquilaria sinensis (Lour.) Spreng: the first chromosome-level draft genome in the Thymelaeceae family.

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