BOTANY
From Mount Etna to the UK: genetics unveil the Oxford ragwort unique journey and resilience
Faculty of Sciences of the University of Lisbon
image:
Senecio squalidus.
view moreCredit: Bruno Nevado
A descendant of Sicilian progenitors, this daisy-family plant appeared in the UK, escaped from a botanical garden, and began its conquest of the region during the Industrial Revolution.
It is rare to uncover the details of a story as fascinating as this, especially since there are few cases where the emergence of a new species can be traced across just 300 years. The Oxford ragwort, Senecio squalidus, a yellow-flowered plant from the daisy family, first appeared in the 17th century at the Oxford Botanic Garden after a crossbreeding of two plants native only to Mount Etna in Sicily.
Bruno Nevado, researcher at the Centre for Ecology, Evolution, and Environmental Changes (CE3C) at the Faculty of Sciences of the University of Lisbon (CIÊNCIAS), leads the study now published in the scientific journal Current Biology. The research reveals key moments in the existence of this species—from its origins to its colonization of the United Kingdom during the Industrial Revolution—through the lens of genetics.
Between the late 17th and early 18th centuries, Senecio chrysanthemifolius and Senecio aethnensis, plants endemic to the rugged slopes of Mount Etna in Italy, were introduced to the gardens of the Duchess of Beaufort in Gloucestershire, England, by botanists Francesco Cupani and William Sherard. On Mount Etna, these plants rarely mingled due to their distinct habitats — S. chrysanthemifolius at altitudes below 1,000 meters and S. aethnensis above 2,000 meters. However, in the UK, conditions brought them into closer proximity, resulting in hybrid individuals. By the first two decades of the 18th century, these hybrids were cultivated in the renowned Oxford Botanic Garden, where they eventually gave rise to a new hybrid species, Senecio squalidus (hence Oxford ragwort). By the end of the 18th century, S. squalidus had escaped its confines and spread into the urban environment of Oxford, beginning its naturalization and eventual colonization of the UK.
Possibly due to its descent from species adapted to the harsh volcanic landscape, this hybrid species managed to thrive, later spreading via the expanding railway network of the Industrial Revolution in the 19th century. It was “by train” that the yellow flowered Oxford ragwort reached nearly every corner of the UK over a span of 150 years. Today, the species can be found from Scotland to Wales, and even in Ireland, thriving along railway lines, roadsides, footpaths, industrial zones, and other disturbed habitats.
Senecio squalidus is one of a few hybrid species with a very recent origin. Bruno Nevado highlights this rarity: “Normally, hybrid species are much older, and it’s difficult to disentangle the processes that contributed to speciation from those that affected the hybrid species later on during its evolution. But with this species, we can study the processes involved in the very early stages of speciation”.
In this new study, conducted in collaboration with researchers from several British universities and the Wellcome Sanger Institute in Cambridge, the genome of S. squalidus was sequenced. Genetic analysis of both S. squalidus and its parental species revealed a rapid reorganization of the hybrid species' genome, driven by the resolution of genetic incompatibilities between the parental species and natural selection. These processes shaped a unique genome, combining traits from both parents, allowing the new species to thrive in an environment where neither parent could survive. Thanks to this unique evolutionary journey, “The Oxford ragwort serves as a small, exceptional laboratory for studying hybridization and its role in the emergence of new species and the colonization of challenging environments,” concludes Bruno Nevado.
Senecio squalidus
Credit
Bruno Nevado
Senecio squalidus
Credit
John Baker
Journal
Current Biology
Article Title
Genomic changes and stabilization following homoploid hybrid speciation of the Oxford ragwort Senecio squalidus
Super golden lettuce richer in vitamin A
A team from the IBMCP (UPV-CSIC) has developed a technique that multiplies the beta-carotene content in plant leaves.
Universitat Politècnica de València
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A team from the IBMCP (UPV-CSIC) has developed a technique that multiplies the beta-carotene content in plant leaves.
view moreCredit: UPV
The work demonstrates that by using biotechnological techniques and treatments with high light intensity, the levels of beta-carotene in leaves can be multiplied up to 30 times by creating new places to store it without affecting vital processes such as photosynthesis. The results are published in the Plant Journal.
Beta-carotene is one of the main carotenoids, pigments found naturally in plants and other photosynthetic organisms that benefit health, with antioxidant, immunostimulant and cognitive-enhancing properties.
Specifically, beta-carotene is the primary precursor of retinoids, chemical compounds with essential bodily functions (vision, cell proliferation and differentiation, immune system...), including vitamin A.
Using tobacco plants (Nicotiana benthamiana) as a laboratory model and lettuce (Lactuca sativa) as a cultivation model, the team led by Manuel Rodríguez Concepción, CSIC researcher at the IBMCP, has managed to increase the beta-carotene content in the leaves without negatively affecting other vital processes such as photosynthesis.
'Leaves need carotenoids such as beta-carotene in the photosynthetic complexes of chloroplasts for their proper functioning,' explains the CSIC researcher. 'When too much or too little beta-carotene is produced in the chloroplasts, they stop functioning, and the leaves eventually die. Our work has successfully produced and accumulated beta-carotene in cellular compartments where it is not normally found by combining biotechnological techniques and treatments with high light intensity,' he summarises.
Higher accumulation and bioaccessibility
The results of this study, published in the Plant Journal, show that it is possible to multiply beta-carotene levels in leaves by creating new places to store them outside the photosynthetic complexes. On the one hand, they have managed to store high levels of beta-carotene in plastoglobules, and fat storage vesicles are naturally present inside chloroplasts. These vesicles do not participate in photosynthesis and do not usually accumulate carotenoids.
‘Stimulating the formation and development of plastoglobules with molecular techniques and intense light treatments not only increases the accumulation of beta-carotene but also its bioaccessibility, i.e. the ease with which it can be extracted from the food matrix to be absorbed by our digestive system,’ says Luca Morelli, first author of the study.
Biofortification of vegetables
The study also shows that beta-carotene synthesis in plastoglobules can be combined with its production outside chloroplasts by means of biotechnological approaches. In this case, co-author Pablo Pérez Colao says, 'beta-carotene accumulates in vesicles similar to plastoglobules but located in the cytosol, the aqueous substance that surrounds the organelles and nucleus of cells’.
The combination of both strategies achieved up to a 30-fold increase in accessible beta-carotene levels compared to untreated leaves. The massive accumulation of beta-carotene also gave the lettuce leaves a characteristic golden colour.
According to the researchers, the discovery that beta-carotene can be produced and stored at very high levels and in a more bioaccessible form outside the places where it is usually found in leaves 'represents a very significant advance for improving nutrition through biofortification of vegetables such as lettuce, chard or spinach without giving up their characteristic scent and flavour'.
Journal
The Plant Journal
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Boosting pro-vitamin A content and bioaccessibility in leaves by combining engineered biosynthesis and storage pathways with high-light treatments
Plant-derived secondary organic aerosols can act as mediators of plant-plant interactions
University of Eastern Finland
A new study published in Science reveals that plant-derived secondary organic aerosols (SOAs) can act as mediators of plant-plant interactions. This research was conducted through the cooperation of chemical ecologists, plant ecophysiologists and atmospheric physicists at the University of Eastern Finland.
It is well known that plants release volatile organic compounds (VOCs) into the atmosphere when damaged by herbivores. These VOCs play a crucial role in plant-plant interactions, whereby undamaged plants may detect warning signals from their damaged neighbours and prepare their defences. “Reactive plant VOCs undergo oxidative chemical reactions, resulting in the formation of secondary organic aerosols (SOAs). We wondered whether the ecological functions mediated by VOCs persist after they are oxidated to form SOAs,” said Dr. Hao Yu, formerly a PhD student at UEF, but now at the University of Bern.
The study showed that Scots pine seedlings, when damaged by large pine weevils, release VOCs that activate defences in nearby plants of the same species. Interestingly, the biological activity persisted after VOCs were oxidized to form SOAs. The results indicated that the elemental composition and quantity of SOAs likely determines their biological functions.
“A key novelty of the study is the finding that plants adopt subtly different defence strategies when receiving signals as VOCs or as SOAs, yet they exhibit similar degrees of resistance to herbivore feeding,” said Professor James Blande, head of the Environmental Ecology Research Group. This observation opens up the possibility that plants have sophisticated sensing systems that enable them to tailor their defences to information derived from different types of chemical cue.
“Considering the formation rate of SOAs from their precursor VOCs, their longer lifetime compared to VOCs, and the atmospheric air mass transport, we expect that the ecologically effective distance for interactions mediated by SOAs is longer than that for plant interactions mediated by VOCs,” said Professor Annele Virtanen, head of the Aerosol Physics Research Group. This could be interpreted as plants being able to detect cues representing close versus distant threats from herbivores.
The study is expected to open up a whole new complex research area to environmental ecologists and their collaborators, which could lead to new insights on the chemical cues structuring interactions between plants.
Journal
Science
Article Title
Biogenic secondary organic aerosol participates in plant interactions and herbivory defense.
Unbiased look at plants uncovers how surprisingly transcription is regulated in plants
Gregor Mendel Institute of Molecular Plant Biology
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A GATC-motif downstream of the transcription start site acts like a rheostat, finetuning transcription in different cell types.
view moreCredit: GMI
Our world today is populated by multicellular organisms, from big trees to climate-wrecking humans. This multicellularity arose independently in plants and animals. Both animals and plants cope differently with the challenges of corralling individual cells together to form a larger organism, such as the need to communicate and coordinate between cells, to share and transport nutrients, and to form specialized structures. One challenge posed by multicellularity is that all cells carry the same genetic code, but the cells look and behave differently: A root cell needs to elongate towards water sources and gravity, while cells in the leaves drive photosynthesis. To achieve different outcomes from the same underlying code, cells tinker with how the code is read out, in what is called transcriptional regulation. Plants and animals also differ fundamentally in how they achieve this transcriptional regulation, as a new paper by the group of Magnus Nordborg at the GMI shows. The results, published in Nature Genetics on September 12, open a new perspective on how plants achieve transcriptional regulation.
New perspective from studying plants
“Much of what we know about transcriptional regulation in plants so far is informed by research on animals and yeast”, says Yoav Voichek, postdoc in the lab of Magnus Nordborg and co-author of the study. “We wanted to look at plants in an unbiased way, thereby making it possible to uncover mechanisms and processes that are unique to plants.” Using a parallel reporter assay in four plant species – maize, Arabidopsis, tomato and Nicotiana benthamiana – the researchers searched for sequences that influence transcription. The transcription start site (TSS) is the specific location on a gene where transcription begins. The researchers identified a region downstream of the TSS that is central for transcriptional regulation.
Looking more closely at how the sequences regulate transcription, the researchers uncovered a novelty in transcriptional regulation. “Most surprisingly, when we swap the position of this regulatory sequence, placing it upstream of the transcriptional start site, it no longer drives transcription”, Voichek says. This finding runs counter to what would be expected from looking at transcriptional regulation in animals: In animals, regulatory sequences are position-independent, as swapping their position does not change how they regulate transcription.
Fine-tuning transcription
Within the regulatory sequence, the scientists uncovered a sequence-motif, consisting of the bases GATC, that strongly drives gene expression. “The sequence motif has a more potent influence on transcription than any DNA motif identified upstream of the transcriptional start site”, Voichek explains. The motif is evolutionarily conserved and found in all vascular plants, i.e. all land plants except for mosses, hornworts and liverworts.
The way in which the GATC-motif influences transcription illustrates how regulatory sequences can fine tune transcription in different cell types. “The higher the number of these motifs downstream of the TSS, the more strongly the gene is expressed”, Voichek says. “The motif acts like a rheostat, finely tuning genes that need to be expressed in all cell types, but at different levels.” In the future, Voichek plans to investigate how the GATC-motif exerts control over transcription. “Our study not only shifts the understanding of transcription regulation in plants but also underscores that we need to study transcription in a diverse set of organisms to broaden our understanding of biology.”
Journal
Nature Genetics
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Widespread position-dependent transcriptional regulatory sequences in plants
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