Christian Braendle

Phenotypic plasticity, genotype-by-environment interactions and genetic assimilation

We focus on the environmental context-dependence of developmental processes (e.g. germ cell proliferation, gametogenesis, dauer formation) to characterize the molecular basis and evolution of phenotypic plasticity. Primarily, we aim to identify developmental and molecular determinants of natural variation in these phenotypes through a combination of quantitative genetic approaches, such as QTL mapping, followed by molecular genetic analyses of uncovered allelic variants and their functional consequences. This research further intends to identify the molecular changes underlying the evolutionary transitions from plastic to fixed trait expression (genetic assimilation). In addition, as genotype-by-environment interactions may also be expressed across multiple generations, we currently characterize genotypic differences in transgenerational transmission of environmentally-induced reproductive defects.   

Genotype-phenotype map: from developmental variation to life history variation

How complex traits, such as life history traits, developmentally emerge through integration of numerous gene-environment, gene-gene interactions, and higher-order interactions among cells and tissues, remains largely unknown. We therefore study the nematode hermaphrodite germline to ask how variation in different parameters of this developmental system translates into variation in reproductive life histories – depending on variable genetic and environmental contexts. Here, one principal goal is to establish causal connections between reaction norms at molecular-developmental levels and reaction norms at the life history level. This research objective includes quantification of allometry and developmental timing of both germline and soma to examine how life history traits are shaped by integration and trade-offs of components of the underlying developmental system architecture.

Developmental robustness and cryptic genetic variation

How do developmental systems generate invariant, reproducible phenotypic outcomes despite environmental variation? We address this question by studying the precision and environmental sensitivity of C. elegans vulval development – a cell fate patterning process governed by a signalling network of Ras, Notch and Wnt pathways. Our past research has shown that correct vulva cell fate patterning is largely maintained across diverse environmental conditions. However, despite such apparent robustness in the phenotypic output, underlying signalling network and cellular mechanisms may show extensive environmental sensitivity. Moreover, we quantify how environmental effects on the system’s precision and signalling network differ within and between species of Caenorhabditis with the aim to better understand cryptic genetic variation and developmental system’s drift. This research thus focuses on the phenomenon of developmental robustness and how an identical phenotypic outcome may arise through cellular and molecular processes that are highly flexible – across environments, genotypes, and species.

Evolution and ecology of Caenorhabditis nematodes


Although C. elegans is increasingly being used in evolutionary studies, there is still very little information on its natural history, ecology, phylogenetic context, and the genetic structure of its naturalpopulations. We therefore contribute to current community efforts to sample and characterize natural Caenorhabditis populations to generate a more comprehensive evolutionary ecological context for C. elegans and its close relatives.