Unraveling the Genetic Basis and Architecture of Rapid Drought Adaptation in Divergent Brassica rapa Populations

• Applicant: Professorin Elena Hamann, Ph.D.
• Subject Area: Plant Genetics and Genomics
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 572621443

Understanding how plants adapt to intensifying drought is critical for predicting responses to rapid climate change. This project investigates the genomic basis of rapid drought adaptation in Brassica rapa using a resurrection approach that compares ancestral and descendant generations from two natural Californian populations that have experienced prolonged drought episodes. Despite parallel phenotypic shifts, particularly in flowering time (FT), water-use efficiency (WUE), and other drought-escape traits, these populations exhibit largely distinct genetic responses. Previous work showed independent allele frequency shifts and divergent gene expression changes, indicating that rapid drought adaptation can arise through different genetic pathways even in closely related populations, posing challenges for predicting evolutionary outcomes. However, we still lack a detailed understanding of the genetic mechanisms underlying these phenotypic shifts, the role of trait correlations, and the extent to which genetic architecture constrains or facilitates adaptive responses. To dissect both the genetic basis and architecture underlying these adaptive shifts, the project integrates a fully factorial common garden experiment with two soil types and watering treatments, quantitative genetics, genome-wide association studies (GWAS), and QTL mapping. Specifically, we aim to (1) assess changes in trait covariation and genotype-by-environment interactions across generations, populations, and treatments; (2) identify the genetic basis of evolutionary trait change and the genetic architecture of traits; and (3) evaluate the extent to which pleiotropy, linkage, and environmental context shape evolutionary constraints or flexibility. Given the complexity of adaptive traits like FT and WUE, our approaches will help disentangle pleiotropic effects from physical linkage among putative causal variants. I hypothesize that pleiotropy is a key driver of trait covariation, with shared loci influencing multiple traits, while population-specific adaptation reflects context-dependent selection on standing variation. This work will reveal novel insights into the genetic mechanisms and architecture of rapid drought adaptation and clarify how genetic constraints and evolutionary flexibility shape adaptation under climate change.

• DFG Programme: Research Grants