The fresh water polyp Hydra belongs to the phylum Cnidaria, which diverged from the metazoan lineage before the appearance of bilaterians. In order to understand the evolution of apoptosis in metazoans, we have begun to elucidate the molecular cell death machinery in this model organism. Based on ESTs and the whole Hydra genome assembly, we have identified 15 caspases. We show that one is activated during apoptosis, four have characteristics of initiator caspases with N-terminal DED, CARD or DD domain and two undergo autoprocessing in vitro. In addition, we describe seven Bcl-2-like and two Bak-like proteins. For most of the Bcl-2 family proteins, we have observed mitochondrial localization. When expressed in mammalian cells, HyBak-like 1 and 2 strongly induced apoptosis. Six of the Bcl-2 family members inhibited apoptosis induced by camptothecin in mammalian cells with HyBcl-2-like 4 showing an especially strong protective effect. This protein also interacted with HyBak-like 1 in a yeast two-hybrid assay. Mutation of the conserved leucine in its BH3 domain abolished both the interaction with HyBak-like 1 and the anti-apoptotic effect. Moreover, we describe novel Hydra BH-3-only proteins. One of these interacted with Bcl-2-like 4 and induced apoptosis in mammalian cells. Our data indicate that the evolution of a complex network for cell death regulation arose at the earliest and simplest level of multicellular organization, where it exhibited a substantially higher level of complexity than in the protostome model organisms Caenorhabditis and Drosophila.

This paper introduces reflection labs as a tool for researcher reflexivity in participatory collaborations. Participatory methodologies intend to achieve equal partnerships, co-production of knowledge and empowerment processes. In this agenda, reflexivity is key, not only for analytical reasons but also to address power inequalities, challenges in the partnerships and other ethical questions. In this paper, we describe the methodological underpinnings and empirical use of a tool we call a ‘reflection lab’. In a 3-year participatory study with refugees (EMPOW), funded by the German Research Foundation, various online and offline spaces were created for reflexivity among community and academic partners. Reflection labs were developed for the academic partners. The term ‘lab’ points to the somewhat experimental nature of this space. Combining different approaches to reflexivity in creative ways, reflection labs offer a space to explore researcher subjectivities. Using field notes, minutes and analytical notes (‘memos’) as a starting point, in-depth discussions foster critical self-reflexivity and provide peer feedback and support about academic researchers’ roles in participatory collaborations. The paper includes an example of a reflection lab that was organized virtually for more than 2 years due to Corona restrictions. By combining aspects of ‘strong reflexivity’ (analyzing researcher subjectivities for epistemic purposes) and ‘ethical reflexivity’ (addressing power inequalities and socio-political implications) reflection labs provide an innovative tool for an engaged, analytical research practice that pursues participatory goals and strives for ethical conduct and accountability.