Metabolomics and Transcriptomics Reveal that Diarylheptanoids Vary in Amomum tsao-ko Fruit Development.

Amomum tsao-ko is an important spice and medicinal plant that has received extensive attention in recent years for its high content of bioactive constituents with the potential for food additives and drug development. Diarylheptanoids are major and characteristic compounds in A. tsao-ko; however, the biochemical and molecular foundation of diarylheptanoids in fruit is unknown. We performed comparative metabolomics and transcriptomics studies in the ripening stages of A. tsao-ko fruit. The chemical constituents of fruit vary in different harvest periods, and the diarylheptanoids have a trend to decrease or increase with fruit development. GO enrichment analysis revealed that plant hormone signaling pathways including the ethylene-activated signaling pathway, salicylic acid, jasmonic acid, abscisic acid, and response to hydrogen peroxide were associated with fruit ripening. The biosynthetic pathways including phenylpropanoid, flavonoids, and diarylheptanoids biosynthesis were displayed in high enrichment levels in ripening fruit. The molecular networking and phytochemistry investigation of A. tsao-ko fruit has isolated and identified 10 diarylheptanoids including three new compounds. The candidate genes related to diarylheptanoids were obtained by coexpression network analysis and phylogenetic analysis. Two key genes have been verified to biosynthesize linear diarylheptanoids. This integrative approach provides gene regulation and networking associated with the biosynthesis of characteristic diarylheptanoids, which can be used to improve the quality of A. tsao-ko as food and medicine.

Chlorine Dioxide Reprograms Rhizosphere Microbial Communities to Enrich Interactions with Tobacco (Nicotiana tabacum).

For decades chlorine dioxide has been used in water disinfection with excellent results. As the scope of application expands, chlorine dioxide has the potential for soil disinfection. We used amplicon sequencing and gas chromatography-mass spectrometry to compare the changes of four mixed rhizosphere microbial community samples and 12 tobacco leaf volatile samples four months after the flood irrigation with chlorine dioxide in different concentrations (0, 2, 4, 8 mg/l). Phenotypic data of 60 tobacco plants were also collected. The effects of chlorine dioxide on rhizosphere microorganisms were positively correlated with dose gradients. Bacteria responded more strongly in both community structure and metabolic pathways than fungi. Five new bacterial phyla (Firmicutes, Bacteroidota, Myxococcota, Patescibacteria, Verrucomicroboata) appeared in chlorine dioxide treatment groups, while the fungal community only appeared as one new fungal phylum (Basidomycota). Alterations in 271 predicted metabolic bacterial pathways were found. However, in the fungal community were only 10 alternations. The correlations between leaf volatile compounds and rhizosphere microorganisms under the influence of chlorine dioxide treatment could be observed based on network results. However, natural connectivity had already been declining rapidly when less than 20% of the network's nodes were removed. Therefore, the microbe-metabolite network is not stable. It might be why chlorine dioxide treatments did not significantly affect tobacco quality (p = 0.754) and phenotype (p = 0.867). As a comprehensive investigation of chlorine dioxide in agriculture, this study proves the effectiveness and safety of chlorine dioxide soil disinfection and widens the application range of chlorine dioxide.

Chromosome-level genome assembly of Amomum tsao-ko provides insights into the biosynthesis of flavor compounds.

Amomum tsao-ko is an economically important spice plant in the ginger family (Zingiberaceae). The dried ripe fruit has been widely used as spice and medicine in Southeast Asia due to its distinct flavor metabolites. However, there is little genomic information available to understand the biosynthesis of its characteristic flavor compounds. Here, we present a high-quality chromosome-level genome of A. tsao-ko with a total length of 2.08 Gb assembled into 24 chromosomes. Potential relationships between genetic variation and chemical constituents were analyzed by a genome-wide association study of 119 representative A. tsao-ko specimens in China. Metabolome and transcriptome correlation analysis of different plant organs and fruit developmental stages revealed the proposed biosynthesis of the characteristic bicyclononane aldehydes and aromatic metabolites in A. tsao-ko fruit. Transcription factors of 20 families may be involved in the regulatory network of terpenoids. This study provides genomic and chemical insights into the biosynthesis of characteristic aroma and flavor constituents, which can be used to improve the quality of A. tsao-ko as food and medicine.