The Max Planck Society awards Bogdan Sieriebriennikov the Otto Hahn medal for his groundbreaking work on phenotypic plasticity. Sieriebriennikov was able to identify the molecular logic and the evolutionary principles of a gene regulatory network that controls how genetically identic nematodes can exhibit distinct phenotypes in different environments. The award ceremony will take place online during the general assembly of the Max Planck Society in June.
Phenotypic plasticity is a key concept in biology, describing the ability of an organism to change its behavior, morphology, and physiology in response to its environment. It allows adaptation to environmental changes within an individual’s life span and is thus thought of as a key mechanism for facing the climate change that scientists expect over the coming decades.
Predators and non-predators sharing the same genome
To explore the environmental influence on development on a molecular basis, Bogdan Sieriebriennikov worked with the model organism Pristionchus pacificus. These nematodes, only one millimeter in length, can have two drastically different mouth forms that determine their way of life: one mouth form restrict the worm to a bacteria-based diet, the other one allows them to prey on other nematode species. Predators and non-predators are genetically indistinguishable, even though their looks and habits differ radically. As established some years ago by Sieriebriennikov’s PhD advisor Ralf Sommer, both genetic and environmental factors trigger an irreversible process during the postembryonic development that decides an individual’s mouth form.
Sommer had shown previously that a single gene, eud-1, is primarily responsible for this developmental switch. "We considered eud-1 to represent just a 'normal' gene in a simple regulatory system," Sommer recollects. "A situation that would change dramatically through Bogdan's work."
An intricate interplay of over 30 genes
Sieriebriennikov first decided to knock out the neighboring genes of eud-1, thereby creating single, double, and quadruple mutants of the tiny worms. He was able to conclude that a complete cluster of genes is involved in mouth form plasticity regulation. These genes are expressed in different sensory neurons, and while some of them make the nematode perceive environmental features that push for a predatory mouth form, others are responsible for perceiving cues that make a non-predatory form more likely. As Sieriebriennikov sums it up: "A whole set of genes is arguing for the key role in environmental perception – and depending on which ones prevail, the nematode will become a predator or feed solely on bacteria."
Perhaps most importantly, Sieriebriennikov studied the interplay of more than 30 genes that govern mouth form plasticity. He identified two transcription factors – proteins directly regulating gene expression – that control the rate of transcription of around 25 genes involved in mouth form plasticity and characterized the function of these target genes.
A framework for future studies
"While developmental plasticity is common and pervasive in biology, it has been ignored for decades," says Sommer. "Neither the environmental influence on development, nor the environmental influence on evolution have been properly integrated into theory." He commends the work of his former PhD student as "a future framework for similar studies of developmental plasticity."
Since 1978, the Otto Hahn Medal of the Max Planck Society is annually awarded to young researchers for outstanding scientific achievements, mostly in connection with their doctorate. The aim of the award is to motivate particularly talented individuals to pursue a university or research career. It is endowed with 7,500 euros of prize money.
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