Chromosome-level genome assembly and resequencing of camphor tree (Cinnamomum camphora) provides insight into phylogeny and diversification of terpenoid and triglyceride biosynthesis of Cinnamomum.

Cinnamomum species attract attentions owing to their scents, medicinal properties, and ambiguous relationship in the phylogenetic tree. Here, we report a high-quality genome assembly of Cinnamomum camphora, based on which two whole-genome duplication (WGD) events were detected in the C. camphora genome: one was shared with Magnoliales, and the other was unique to Lauraceae. Phylogenetic analyses illustrated that Lauraceae species formed a compact sister clade to the eudicots. We then performed whole-genome resequencing on 24 Cinnamomum species native to China, and the results showed that the topology of Cinnamomum species was not entirely consistent with morphological classification. The rise and molecular basis of chemodiversity in Cinnamomum were also fascinating issues. In this study, six chemotypes were classified and six main terpenoids were identified as major contributors of chemodiversity in C. camphora by the principal component analysis. Through in vitro assays and subcellular localization analyses, we identified two key terpene synthase (TPS) genes (CcTPS16 and CcTPS54), the products of which were characterized to catalyze the biosynthesis of two uppermost volatiles (i.e. 1,8-cineole and (iso)nerolidol), respectively, and meditate the generation of two chemotypes by transcriptional regulation and compartmentalization. Additionally, the pathway of medium-chain triglyceride (MCT) biosynthesis in Lauraceae was investigated for the first time. Synteny analysis suggested that the divergent synthesis of MCT and long-chain triglyceride (LCT) in Lauraceae kernels was probably controlled by specific medium-chain fatty acyl-ACP thioesterase (FatB), type-B lysophosphatidic acid acyltransferase (type-B LPAAT), and diacylglycerol acyltransferase 2b (DGAT 2b) isoforms during co-evolution with retentions or deletions in the genome.

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The variations in plant growth of 32 Quercus acutissima provenances in three sites (Yongfeng, Jiangxi; Kaihua, Zhejiang and Chuzhou, Anhui) were studied. The AMMI model was used to analyze the stability of growth traits and to select the best provenances. The results showed that tree height, diameter at breast (ground) height, and aboveground biomass (AGB) per individual of the provenances were significantly different in the three sites. The AGB per individual was significantly affected by site, provenance, and the interaction of provenance × site. Site had the greatest impact on the variation of tree growth, followed by provenance and provenance × site. The growth performance of these superior provenances in different sites varied greatly in the seedling stage (1-3 years old) and young forest stage (4-11 years old). Based on the AGB per individual in the 11st year, the best provenances were selected in each site. Seven superior provenances of Yongfeng, Jiangxi were selected, with the average AGB per individual increased by 15.6%-57.8% compared with the ave-rage value. Seven superior provenances of Kaihua, Zhejiang were selected, with the average AGB per individual increased by 19.2%-45.2%. Eight superior provenances of Chuzhou, Anhui were selected,with the average AGB per individual increased by 24.9%-63.3%. According to the growth performance and stability, four superior provenances were selected to develop short-rotation charcoal forest cultivation across three sites, with an average AGB per individual of 36.55 kg and an average stability parameter of 0.97.

The Litsea genome and the evolution of the laurel family.

The laurel family within the Magnoliids has attracted attentions owing to its scents, variable inflorescences, and controversial phylogenetic position. Here, we present a chromosome-level assembly of the Litsea cubeba genome, together with low-coverage genomic and transcriptomic data for many other Lauraceae. Phylogenomic analyses show phylogenetic discordance at the position of Magnoliids, suggesting incomplete lineage sorting during the divergence of monocots, eudicots, and Magnoliids. An ancient whole-genome duplication (WGD) event occurred just before the divergence of Laurales and Magnoliales; subsequently, independent WGDs occurred almost simultaneously in the three Lauralean lineages. The phylogenetic relationships within Lauraceae correspond to the divergence of inflorescences, as evidenced by the phylogeny of FUWA, a conserved gene involved in determining panicle architecture in Lauraceae. Monoterpene synthases responsible for production of specific volatile compounds in Lauraceae are functionally verified. Our work sheds light on the evolution of the Lauraceae, the genetic basis for floral evolution and specific scents.

The complete mitochondrial genomes of two sibling species of camellia weevils (Coleoptera: Curculionidae) and patterns of Curculionini speciation.

Complete mitochondrial genomes contain large and diverse datasets for species delineation. To better understand the divergence of the two morphologically indistinguishable weevil species in Curculionini, we first sequenced and compared their complete mitochondrial genomes. The complete mitochondrial genomes of Curculio chinensis and Curculio sp. were 19,713 bp with an A + T content of 76.61% and 19,216 bp with an A + T content of 76.85%, respectively. All 37 of the typical mitochondrial genes were determined in both species. The 13 protein sequences of the two species shared high homology (about 90%) except for ATP8 (73.08%). The differences in secondary structure of ATP8 were the number of possible proteins and nucleic acid binding sites. There were 22 and 15 mismatched base-pairs in the tRNA secondary structures from C. chinensis and Curculio sp., respectively. Maximum Likelihood and Bayesian analyses indicated that Curculio sp. is a novel species closely related to C. chinensis. The divergence time estimation suggests that Cryptorhynchinae and Curculionini lines diverged in the Cenozoic Period, while C. chinensis and Curculio sp. diverged at 6.7079 (95% CI 5-13) Mya. This study demonstrates the utility of using complete mitochondrial gene sets for phylogenetic analysis and enhances our understanding of the genetic basis for the evolution of the Curculionini.

An efficient noble-metal-free supported copper catalyst for selective nitrocyclohexane hydrogenation to cyclohexanone oxime.

It was shown for the first time that cyclohexanone oxime (CHO) can be selectively produced by heterogeneous copper-catalyzed hydrogenative transformation of nitrocyclohexane (NC). The combination of Cu0 and Cu+ and their cooperative interaction with weakly acidic SiO2 supports elicited a significantly unique and selective catalysis in the hydrogenation of NC to CHO.

Transcriptome sequencing and expression analysis of terpenoid biosynthesis genes in Litsea cubeba.

BACKGROUND: Aromatic essential oils extracted from fresh fruits of Litsea cubeba (Lour.) Pers., have diverse medical and economic values. The dominant components in these essential oils are monoterpenes and sesquiterpenes. Understanding the molecular mechanisms of terpenoid biosynthesis is essential for improving the yield and quality of terpenes. However, the 40 available L. cubeba nucleotide sequences in the public databases are insufficient for studying the molecular mechanisms. Thus, high-throughput transcriptome sequencing of L. cubeba is necessary to generate large quantities of transcript sequences for the purpose of gene discovery, especially terpenoid biosynthesis related genes. RESULTS: Using Illumina paired-end sequencing, approximately 23.5 million high-quality reads were generated. De novo assembly yielded 68,648 unigenes with an average length of 834 bp. A total of 38,439 (56%) unigenes were annotated for their functions, and 35,732 and 25,806 unigenes could be aligned to the GO and COG database, respectively. By searching against the Kyoto Encyclopedia of Genes and Genomes Pathway database (KEGG), 16,130 unigenes were assigned to 297 KEGG pathways, and 61 unigenes, which contained the mevalonate and 2-C-methyl-D-erythritol 4-phosphate pathways, could be related to terpenoid backbone biosynthesis. Of the 12,963 unigenes, 285 were annotated to the terpenoid pathways using the PlantCyc database. Additionally, 14 terpene synthase genes were identified from the transcriptome. The expression patterns of the 16 genes related to terpenoid biosynthesis were analyzed by RT-qPCR to explore their putative functions. CONCLUSION: RNA sequencing was effective in identifying a large quantity of sequence information. To our knowledge, this study is the first exploration of the L. cubeba transcriptome, and the substantial amount of transcripts obtained will accelerate the understanding of the molecular mechanisms of essential oils biosynthesis. The results may help improve future genetic and genomics studies on the molecular mechanisms behind the chemical composition of essential oils in L. cubeba fruits.

FAD2-DGAT2 genes coexpressed in endophytic Aspergillus fumigatus derived from tung oilseeds.

Recent efforts to genetically engineer plants that contain fatty acid desaturases to produce valuable fatty acids have made only modest progress. Diacylglycerol acyltransferase 2 (DGAT2), which catalyzes the final step in triacylglycerol (TAG) assembly, might potentially regulate the biosynthesis of desired fatty acids in TAGs. To study the effects of tung tree (Vernicia fordii) vfDGAT2 in channeling the desired fatty acids into TAG, vfDGAT2 combined with the tung tree fatty acid desaturase-2 (vfFAD2) gene was co-introduced into Aspergillus fumigatus, an endophytic fungus isolated from healthy tung oilseed. Two transformants coexpressing vfFAD2 and vfDGAT2 showed a more than 6-fold increase in linoleic acid production compared to the original A. fumigatus strain, while a nearly 2-fold increase was found in the transformant expressing only vfFAD2. Our data suggest that vfDGAT2 plays a pivotal role in promoting linoleic acid accumulation in TAGs. This holds great promise for further genetic engineering aimed at producing valuable fatty acids.