Prof. Dr. Ralf Sommer (MPI Tübingen)

Prof. Dr. Ralf Sommer talks about “The secrets of predatory feeding plasticity in nematodes: Microbiome, epigenetics and kin selection”.

Abstract:

Developmental plasticity is increasingly recognized as primary mechanism for the emergence of novelty. However, molecular mechanisms underlying this phenomenon remain elusive. The nematode Pristionchus pacificus exhibits developmental plasticity of its mouth-form and feeding strategies. Individuals develop one of two alternative mouth-forms, a predatory eurystomatous (Eu, wide-mouthed) or a bacteriovorous stenostomatous (St, narrow-mouthed) form. Using genetic screens we have identified developmental switch genes that regulated plasticity. eud-1 mutants are all-St, whereas mutants in the downstream nuclear-hormone-receptor nhr-40 are all-Eu. More recent work indicates that eud-1 is part of a multi-gene locus with some supergene characteristics. Furthermore, eud-1 expression is under epigenetic control involving the histone acetyltransferase lsy-12 and an antisense RNA at the eud-1 locus itself that up-regulates eud-1 expression.

Here, I will present some of our most recent findings. First, the analysis of the microbiome of wild-derived P. pacificus strains revealed a plethora of bacteria, several of which can be cultured in the lab. Interestingly, some of these microbes influence diverse aspects of mouth-form plasticity and predation, including some that induce surplus killing: a phenomenon where P. pacificus worms exhibit extreme killing of other nematodes without feeding on the corpses of these animals. I will describe our recent findings regarding the underlying mechanisms of this behavior. Second, I will discuss the epigenetics of plasticity and finally, will describe novel findings regarding self-recognition and kin selection in this predatory species.