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Many studies have shown that individuals from invasive populations of many different plant species grow larger than individuals from native populations and that this difference has a genetic basis. This increased vigor in invasive populations is thought to be due to life history tradeoffs, in which selection favors the loss of costly defense traits, thereby freeing resources that can be devoted to increased growth or fecundity. Despite the theoretical importance of such allocation shifts for invasions, there have been no efforts to understand apparent evolutionary shifts in defensegrowth allocation mechanistically. Real location of nitrogen (N) to photosynthesis is likely to play a crucial role in any growth increase; however, no study has been conducted to explore potential evolutionary changes in N allocation of introduced plants. Here, we show that introduced Ageratina adenophora. a noxious invasive plant throughout the subtropics, appears to have evolved increased N allocation to photosynthesis (growth) and reduced allocation to cell walls, resulting in poorer structural defenses. Our results provide a potential mechanism behind the commonly observed and genetically based increase in plant growth and vigor when they are introduced to new ranges.

Crofton weed (Ageratina adenophora) is one of the most hazardous invasive plant species, which causes serious economic losses and environmental damages worldwide. However, the sequence resource and genome information of A. adenophora are rather limited, making phylogenetic identification and evolutionary studies very difficult. Here, we report the complete sequence of the A. adenophora chloroplast (cp) genome based on Illumina sequencing. The A. adenophora cp genome is 150, 689 bp in length including a small single-copy (SSC) region of 18, 358 bp and a large single-copy (LSC) region of 84, 815 bp separated by a pair of inverted repeats (IRs) of 23, 755 bp. The genome contains 130 unique genes and 18 duplicated in the IR regions, with the gene content and organization similar to other Asteraceae cp genomes. Comparative analysis identified five DNA regions (ndhD-ccsA, psbI-trnS, ndhF-ycf1, ndhI-ndhG and atpA-trnR) containing parsimony-informative characters higher than 2%, which may be potential informative markers for barcoding and phylogenetic analysis. Repeat structure, codon usage and contraction of the IR were also investigated to reveal the pattern of evolution. Phylogenetic analysis demonstrated a sister relationship between A. adenophora and Guizotia abyssinica and supported a monophyly of the Asterales. We have assembled and analyzed the chloroplast genome of A. adenophora in this study, which was the first sequenced plastome in the Eupatorieae tribe. The complete chloroplast genome information is useful for plant phylogenetic and evolutionary studies within this invasive species and also within the Asteraceae family.

KEY MESSAGE : EaCHS1 functions in the tolerance of plantlets to salinity stress by maintaining ROS homeostasis. Chalcone synthase (CHS) is an essential enzyme in the biosynthesis of flavonoids. Expression of CHS is governed by a wide range of environmental stimuli, including UV light, pathogen attack, and circadian clocks. However, little research exists on the relationship between CHS and salinity stress. In this work, we constructed separate overexpression and RNA interference vectors of EaCHS1, and transferred them into tobacco. Overexpression of EaCHS1 increased the production of downstream flavonoids and the expressions of related genes in the phenylpropanoid pathway. It also improved resistance to salinity stress during seed germination and root development. In contrast, heterologous silencing of endogenous CHS in tobacco by a conserved EaCHS1 fragment had opposite effect. Together, our results indicated that changing the expression level of EaCHS1 in plants alters the accumulation of flavonoids and regulates plantlet tolerance to salinity stress by maintaining ROS homeostasis.

Summary Crofton weed ( Ageratina adenophora ), a significant invasive species, extensively disrupts ecosystem stability, leading to considerable economic losses. However, genetic insights into its invasive mechanisms have been limited by a lack of genomic data. In this study, we present the successful de novo assembly of the triploid genome of A. adenophora , leveraging long-read PacBio Sequel, optical mapping, and Hi-C sequencing. Our assembly resolved into a haplotype-resolved genome comprising 51 chromosomes, with a total size of ~3.82 Gb and a scaffold N50 of 70.8 Mb. BUSCO analysis confirmed the completeness of 97.71% of genes. Genome annotation revealed 3.16 Gb (76.44%) of repetitive sequences and predicted 123,134 protein-coding genes, with 99.03% functionally annotated. The high-quality reference genome will provide valuable genomic resources for future studies on the evolutionary dynamics and invasive adaptations of A. adenophora .

Trait differences between invasive and native species are believed to be closely related to whether the former are successful. However, few studies have measured trait differences between invasive and native species directly under field conditions or during long term experiments. We examined the phenological pattern, plant height and biomass accumulation and allocation of Crofton weed (Eupatorium adenophorum Spreng.) and co-occurring native species in a community during a three-year succession. The phenological pattern of Crofton weed differed from that of co-occurring native species. Crofton weed had longer vegetative stage (when resources were more available), a higher biomass accumulation and a higher above/below-ground ratio compared to native species. Crofton weed was shorter than grasses and two forbs (Artemisia tangutica and Cynoglossum amabile) during its first year of growth, but was significantly taller than all other species during subsequent years. The dominance (calculated as the importance value) of Crofton weed was the highest among all other species and continually increased over time while the dominance of co-occurring native species decreased. This study provides direct field evidence that trait differences are important to plant invasion.

In order to ascertain the invasive mechanism and control strategy of the invasive Crofton weed, Ageratina adenophora , its ecological adaptability and population differentiation, the formation of single dominant population, displacement of native plants and sustainable management strategies were investigated. The present results helped to clarify and explain such issues as the adaptability post invasion, interaction and competition between inter- and intra-species and community resistance, thereby providing important references to researches on other invasive alien species.

In this study, conserved sequence regions of HMGR , DXR , and CHS (encoding 3-hydroxy-3-methylglutaryl-CoA reductase, 1-deoxyxylulose-5-phosphate reductoisomerase and chalcone synthase, respectively) were amplified by reverse transcriptase (RT)-PCR from Eupatorium adenophorum . Quantitative real-time PCR showed that the expression of CHS was related to the level of HHO, an allelochemical isolated from E. adenophorum . Semi-quantitative RT-PCR showed that there was no significant difference in expression of genes among three different tissues, except for CHS . Southern blotting indicated that at least three CHS genes are present in the E. adenophorum genome. A full-length cDNA from CHS genes (named EaCHS1 , GenBank ID: FJ913888) was cloned. The 1,455 bp cDNA contained an open reading frame (1,206 bp) encoding a protein of 401 amino acids. Preliminary bioinformatics analysis of EaCHS1 revealed that EaCHS1 was a member of CHS family, the subcellular localization predicted that EaCHS1 was a cytoplasmic protein. To the best of our knowledge, this is the first report of conserved sequences of these genes and of a full-length EaCHS1 gene in E. adenophorum . The results indicated that CHS gene is related to allelopathy of E. adenophorum .

A novel bacteria strain, designated YIM B02787 , was isolated from rhizosphere soil of Ageratina adenophora, in Yunnan, southwest China. The strain was aerobic, Gram-stain-negative, rod-shaped and motile with one polar flagellum. Growth occurred at 4-45 °C (optimum, 20-30 °C) and pH 6.0-10.0 (optimum, 7.0-8.0), and in presence of 0-1% (w/v) NaCl. Phylogenetic analyses based on both 16S rRNA gene and genome sequences data revealed that strain YIM B02787 belongs to the genus Massilia, being closely related to Massilia phosphatilytica KCTC 52513 (98.93% similarity), M. putida KCTC 42761 (98.86%), and M. kyonggiensis JCM 19189 (98.78%). The DNA G+C content was 65.9%. The digital DNA-DNA hybridization and average nucleotide identity values between the isolate strain and aforementioned closely neighbors were low, at 35.8-48.9 and 88.5-92.5%, respectively. Strain YIM B02787 contained Q-8 as the ubiquinone and major fatty acids were summed feature 3 (C ω7c and/or C ω6c, 45.5%) and C (27.5%). The polar lipid profile consisted of phosphatidylglycerol, phosphatidylethanolamine, diphosphatidylglycerol, two unidentified phospholipids, two unidentified aminophospholipids, and one unidentified polar lipid. On the basis of its phylogenetic, phenotypic and chemotaxonomic characteristics, strain YIM B02787 represents a novel species of the genus Massilia, for which the name Massilia orientalis sp. nov. is proposed. The type strain is YIM B02787 (= NBRC 116628  = CGMCC 1.61539 ).

Artemisia frigida Willd. is an important Mongolian traditional medicinal plant with pharmacological functions of stanch and detumescence. However, there is little sequence and genomic information available for Artemisia frigida , which makes phylogenetic identification, evolutionary studies, and genetic improvement of its value very difficult. We report the complete chloroplast genome sequence of Artemisia frigida based on 454 pyrosequencing. The complete chloroplast genome of Artemisia frigida is 151,076 bp including a large single copy (LSC) region of 82,740 bp, a small single copy (SSC) region of 18,394 bp and a pair of inverted repeats (IRs) of 24,971 bp. The genome contains 114 unique genes and 18 duplicated genes. The chloroplast genome of Artemisia frigida contains a small 3.4 kb inversion within a large 23 kb inversion in the LSC region, a unique feature in Asteraceae. The gene order in the SSC region of Artemisia frigida is inverted compared with the other 6 Asteraceae species with the chloroplast genomes sequenced. This inversion is likely caused by an intramolecular recombination event only occurred in Artemisia frigida . The existence of rich SSR loci in the Artemisia frigida chloroplast genome provides a rare opportunity to study population genetics of this Mongolian medicinal plant. Phylogenetic analysis demonstrates a sister relationship between Artemisia frigida and four other species in Asteraceae, including Ageratina adenophora, Helianthus annuus, Guizotia abyssinica and Lactuca sativa, based on 61 protein-coding sequences. Furthermore, Artemisia frigida was placed in the tribe Anthemideae in the subfamily Asteroideae (Asteraceae) based on ndhF and trnL-F sequence comparisons. The chloroplast genome sequence of Artemisia frigida was assembled and analyzed in this study, representing the first plastid genome sequenced in the Anthemideae tribe. This complete chloroplast genome sequence will be useful for molecular ecology and molecular phylogeny studies within Artemisia species and also within the Asteraceae family.

Pathogen accumulation after introduction is unavoidable for exotic plants over a long period of time. Therefore, it is important to understand whether plant invasion promotes novel pathogen emergence and increases the risk of pathogen movement among agricultural, horticultural, and wild native plants. In this study, we used multiple gene analysis to characterize the species composition of 104 isolates of Alternaria obtained from the invasive plant Ageratina adenophora and native plants from Yunnan, Hubei, Guizhou, Sichuan, and Guangxi in China. Phylogenetically, these strains were from A. alternata (88.5%), A. gossypina (10.6%) and A. steviae (0.9%). There was a high amount of sharing between strains associated with A. adenophora and with local plants. Pathogenicity tests indicated that most of these Alternaria strains are generalists; the isolates with a wider host range were more virulent to the plant. Woody plants were more resistant to these strains than herbaceous plants and vines. However, the invasive plant A. adenophora was highly sensitive to these strains. Our data are valuable for understanding how A. adenophora invasion impacts the Alternaria species composition of the native plant and whether A. adenophora invasion causes potential disease risks in invaded ecosystems.