Explore the vast range of titles available.

Key messageSsLOS directly catalyzed formation of the sesquiterpenoid ether liguloxide in the medicinal plant Senecio scandens.Terpene synthases determine the diversity of terpene skeletons and corresponding terpenoid natural products. Oxygenated groups introduced in catalysis of terpene synthases are important for solubility, potential bioactivity and further elaboration of terpenoids. Here we identified one terpene synthase, SsLOS, in the Chinese medicinal plant Senecio scandens. SsLOS acted as the sesquiterpene synthase and utilized (E,E)-farnesyl diphosphate as the substrate to produce a blend of sesquiterpenoids. GC–MS analysis and NMR structure identification demonstrated that SsLOS directly produced the sesquiterpenoid ether, liguloxide, as well as its alcoholic isomer, 6-epi-guaia-2(3)-en-11-ol. Homology modeling and site-directed mutagenesis were combined to explore the catalytic mechanism of SsLOS. A few key residues were identified in the active site and hedycaryol was identified as the neutral intermediate of SsLOS catalysis. The plausible catalytic mechanism was proposed as well. Altogether, SsLOS was identified and characterized as the sesquiterpenoid ether synthase, which is the second terpenoid ether synthase after 1,8-cineol synthase, suggesting some insights for the universal mechanism of terpene synthases using the water molecule in the catalytic cavity.

Hybridization between species can lead to introgression of genes from one species to another, providing a potential mechanism for preserving and recombining key traits during evolution. To determine the molecular basis of such transfers, we analyzed a natural polymorphism for flower-head development in SENECIO: We show that the polymorphism arose by introgression of a cluster of regulatory genes, the RAY locus, from the diploid species S. squalidus into the tetraploid S. vulgaris. The RAY genes are expressed in the peripheral regions of the inflorescence meristem, where they promote flower asymmetry and lead to an increase in the rate of outcrossing. Our results highlight how key morphological and ecological traits controlled by regulatory genes may be gained, lost, and regained during evolution.

Western flower thrips (Frankliniella occidentalis) has become a key insect pest of agricultural and horticultural crops worldwide. Little is known about host plant resistance to thrips. In this study, we investigated thrips resistance in F ₂ hybrids of Senecio jacobaea and Senecio aquaticus. We identified thrips-resistant hybrids applying three different bioassays. Subsequently, we compared the metabolomic profiles of these hybrids applying nuclear magnetic resonance spectroscopy (NMR). The new developments of NMR facilitate a wide range coverage of the metabolome. This makes NMR especially suitable if there is no a priori knowledge of the compounds related to herbivore resistance and allows a holistic approach analyzing different chemical compounds simultaneously. We show that the metabolomes of thrips-resistant and -susceptible hybrids differed considerably. Thrips-resistant hybrids contained higher amounts of the pyrrolizidine alkaloids (PA), jacobine, and jaconine, especially in younger leaves. Also, a flavanoid, kaempferol glucoside, accumulated in the resistant plants. Both PAs and kaempferol are known for their inhibitory effect on herbivores. In resistant and susceptible F ₂ hybrids, young leaves showed less thrips damage than old leaves. Consistent with the optimal plant defense theory, young leaves contained increased levels of primary metabolites such as sucrose, raffinose, and stachyose, but also accumulated jacaranone as a secondary plant defense compound. Our results prove NMR as a promising tool to identify different metabolites involved in herbivore resistance. It constitutes a significant advance in the study of plant-insect relationships, providing key information on the implementation of herbivore resistance breeding strategies in plants.

Herbarium accession data offer a useful historical botanical perspective and have been used to track the spread of plant invasions through time and space. Nevertheless, few studies have utilised this resource for genetic analysis to reconstruct a more complete picture of historical invasion dynamics, including the occurrence of separate introduction events. In this study, we combined nuclear and chloroplast microsatellite analyses of contemporary and historical collections of Senecio madagascariensis, a globally invasive weed first introduced to Australia c. 1918 from its native South Africa. Analysis of nuclear microsatellites, together with temporal spread data and simulations of herbarium voucher sampling, revealed distinct introductions to south-eastern Australia and mid-eastern Australia. Genetic diversity of the south-eastern invasive population was lower than in the native range, but higher than in the mid-eastern invasion. In the invasive range, despite its low resolution, our chloroplast microsatellite data revealed the occurrence of new haplotypes over time, probably as the result of subsequent introduction(s) to Australia from the native range during the latter half of the 20th century. Our work demonstrates how molecular studies of contemporary and historical field collections can be combined to reconstruct a more complete picture of the invasion history of introduced taxa. Further, our study indicates that a survey of contemporary samples only (as undertaken for the majority of invasive species studies) would be insufficient to identify potential source populations and occurrence of multiple introductions.

Hybridisation is well documented in many species, especially plants. Although hybrid populations might be short-lived and do not evolve into new lineages, hybridisaiton could lead to evolutionary novelty, promoting adaptation and speciation. The genus Senecio (Asteraceae) has been actively used to unravel the role of hybridisation in adaptation and speciation. In this article, we first briefly describe the process of hybridisation and the state of hybridisation research over the years. We then discuss various roles of hybridisation in plant adaptation and speciation illustrated with examples from different Senecio species, but also mention other groups of organisms whenever necessary. In particular, we focus on the genomic and transcriptomic consequences of hybridisation, as well as the ecological and physiological aspects from the hybrids’ point of view. Overall, this article aims to showcase the roles of hybridisation in speciation and adaptation, and the research potential of Senecio , which is part of the ecologically and economically important family, Asteraceae.

Senecio squalidus (Asteraceae) currently includes nine subspecies distributed in North and Central Europe and in the Mediterranean basin. Within this taxonomic aggregate, many species have been described, but research on their nomenclatural types is incomplete. A complete nomenclatural survey of 19 names belonging to this taxonomically critical group was carried out. Fourteen lectotypes are here designated. The nomenclatural analysis, complemented by field investigations in the type localities of the taxa described in the Central Mediterranean, allowed us to accept 10 species. Accordingly, we proposed here a new name and a new missing combination at a specific level: S. aknoulensis and S. calabrus.

All members of Asteraceae, the largest flowering family, have a unique compressed inflorescence known as a capitulum, which resembles a solitary flower. The capitulum often consists of bilateral (zygomorphic) ray florets and radial (actinomorphic) disc florets. In Antirrhinum majus, floral zygomorphy is established by the interplay between dorsal petal identity genes, CYCLOIDEA (CYC) and RADIALIS (RAD), and a ventral gene DIVARICATA (DIV). To investigate the role of CYC, RAD, and DIV in the development of ray and disc florets within a capitulum, we isolated homologs of these genes from an Asteraceae species, Senecio vulgaris (common groundsel). After initial uniform expression of RAY3 (CYC), SvRAD, and SvDIV1B in ray florets only, RAY3 and SvRAD were exclusively expressed in the ventral petals of the ray florets. Our functional analysis further showed that RAY3 promotes and SvDIV1B represses petal growth, confirming their roles in floral zygomorphy. Our results highlight that while floral symmetry genes such as RAY3 and SvDIV1B appear to have a conserved role in petal growth in both Senecio and Antirrhinum, the regulatory relationships and expression domains are divergent, allowing ventral petal elongation in Senecio versus dorsal petal elongation in Antirrhinum In S vulgaris, diversification of CYC genes has led to novel interactions; SvDIV1B inhibits RAY3 and SvRAD, and may activate RAY2 This highlights how recruitment of floral symmetry regulators into dynamic networks was crucial for creating a complex and elaborate structure such as the capitulum.

Ecological differentiation is recognized as an important factor for polyploid speciation, but little is known regarding whether the ecological niches of cytotypes differ between areas of sympatry and areas where single cytotypes occur (i.e. niche displacement). Ecological niches of four groups of Senecio carniolicus sensu lato (s.l.) (western and eastern diploid lineages, tetraploids and hexaploids) were characterized via Landolt indicator values of the accompanying vascular plant species and tested using multivariate and univariate statistics. The four groups of S. carniolicus s.l. were ecologically differentiated mainly with respect to temperature, light and soil (humus content, nutrients, moisture variability). Niche breadths did not differ significantly. In areas of sympatry hexaploids shifted towards sites with higher temperature, less light and higher soil humus content as compared with homoploid sites, whereas diploids and tetraploids shifted in the opposite direction. In heteroploid sites of tetraploids and the western diploid lineage the latter shifted towards sites with lower humus content but higher aeration. Niche displacement can facilitate the formation of stable contact zones upon secondary contact of polyploids and their lower-ploid ancestors and/or lead to convergence of the cytotypes' niches after they have attained non-overlapping ranges. Niche displacement is essential for understanding ecological consequences of polyploidy.

Senecio vulgaris L. (Asteraceae), a European-origin invasive plant, has established widespread populations in China since the nineteenth century, posing both ecological and health-related threats due to its herbicide resistance, toxic pyrrolizidine alkaloids, and broad habitat adaptability. Despite being classified as a Level 4 invasive species in China, its potential risk remains underestimated. In this study, we applied an optimized MaxEnt model using occurrence data from both native (Europe) and invasive (China) ranges to predict the species’ potential distribution. Our results revealed high environmental suitability in central, eastern, southwestern, and northeastern China, with human activity, temperature, and precipitation as dominant predictors. Niche analysis indicated that S. vulgaris in China occupies environmental conditions largely overlapping with its native niche, demonstrating niche conservatism rather than expansion. These findings suggest that even moderately ranked invasive species can maintain ecological stability while gradually expanding, especially under increasing anthropogenic pressure. Our results underscore the need for targeted monitoring and preemptive management in agriculturally sensitive regions. This study provides a practical framework for assessing and managing adaptable invasive plants beyond those classified as high risk.

Speciation with gene flow, or the evolution of reproductive isolation between interbreeding populations, remains a controversial problem in evolution. This is because gene flow erodes the adaptive differences that selection creates between populations. Here, we use a combination of common garden experiments in the field and in the glasshouse to investigate what ecological and genetic mechanisms prevent gene flow and maintain morphological and genetic differentiation between coastal parapatric populations of the Australian groundsel Senecio lautus. We discovered that in each habitat extrinsic reproductive barriers prevented gene flow, whereas intrinsic barriers in F₁ hybrids were weak. In the field, herbivores played a major role in preventing gene flow, but glasshouse experiments demonstrated that soil type also created variable selective pressures both locally and on a greater geographic scale. Our experimental results demonstrate that interfertile plant populations adapting to contrasting environments may diverge as a consequence of concurrent natural selection acting against migrants and hybrids through multiple mechanisms. These results provide novel insights into the consequences of local adaptation in the origin of strong barriers to gene flow in plants, and suggest that herbivory may play an important role in the early stages of plant speciation.