Friday, September 20, 2024

 BOTANY

From Mount Etna to the UK: genetics unveil the Oxford ragwort unique journey and resilience




Faculty of Sciences of the University of Lisbon
Senecio squalidus 

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Senecio squalidus.

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Credit: 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


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

Super golden lettuce richer in vitamin A 

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A team from the IBMCP (UPV-CSIC) has developed a technique that multiplies the beta-carotene content in plant leaves.

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Credit: 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'.

 

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