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 toward 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.

“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.”

A small team of biologists at Mississippi State University and the University of Wyoming has found a species of parasitoid wasp that lays its eggs inside of living adult fruit flies. In their study, published in the journal Nature, the group accidentally discovered the new wasp species while conducting research on fruit flies.

Prior research has shown that there are large numbers of parasitoid species, many of which rely on a host to carry their eggs for them. A large number of wasp species lay their eggs in fruit fly larvae or pupae. In such instances, the eggs remain dormant in the host for a certain period of time as they mature and then begin eating the host from the inside until they are fully grown, generally resulting in the death of the host.

In this new study, the research team has found one species of wasp that lays its eggs inside the body of a fully grown fruit fly.

The work researchers were collecting adult fruit flies from the backyard of one of the team members—their intent was to learn more about nematode infections in the flies. While studying some of the specimens they caught, they found eggs in their abdomens that they were unable to identify. A closer look showed that they were from a previously unknown species of wasp.

The researchers studied the eggs and the wasps at various stages of their life cycle and found that they were related to wasps in the genus Syntretus—all of the others in the genus parasitize only adult bees and wasps. They named the new species Syntretus perlmani.

The research team suggests the newly found species switched from parasitizing bees and wasps to adult fruit flies for unknown reasons. Also unknown are the changes the wasps underwent that allowed for the switch—and how the wasps manage to catch and hold on to the fruit flies, which are notoriously elusive.

The team suggests their findings and observations could lead to new avenues of research into parasitoidism of adult insects.

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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 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. 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 Nevado.