Assistant Professor Purdue University West Lafayette, Indiana
Body of Abstract: Completion of the genotype-phenotype-fitness map is an ultimate, but unrealized, goal of the study of adaptation. What is lacking are examples of the full causal chain connecting naturally occurring sequence polymorphisms, molecular and organismal phenotypes, and fitness in the contrasting environments in which the plants evolved. Here we use locally adapted ecotypes of Arabidopsis thaliana from Italy (IT) and Sweden (SW) to investigate the fitness consequences of a polymorphism at CBF2, which encodes a key regulator of cold-acclimated freezing tolerance. The functional SW allele of CBF2 is important for overwinter survival in Sweden, and CBF2 is hypothesized to be a mechanism for genotype-by-environment interactions for fitness in nature. We estimated the effects of CBF2 on survival and fruit production at the native field sites over five years, comparing fitness of parental ecotypes to that of near isogenic lines with segments containing alternate alleles of CBF2 in both genetic backgrounds. Single gene resolution of these effects was then obtained using growth chamber experiments mimicking environmental conditions at the two sites and comparing fitness of parental ecotypes to both cbf2 loss of function mutation lines in a SW background, and transgenic lines containing the functional SW CBF2 allele and native promoter in an IT background. There were significant and substantial fitness consequences (7-21% reduction in lifetime fitness) of having the “wrong” CBF2 allele at both field sites and in both growth chamber environments, thus we clearly demonstrate a link between naturally occurring sequence polymorphism and fitness in realistic environments. Current NSF funded work (contact me about available positions in the lab!) will determine the genetic and physiological mechanisms of CBF2 mediated cold acclimation, and the costs of such acclimation, using transcriptomic and metabolomic approaches on parental ecotypes and engineered lines during cold acclimation conditions in growth chamber experiments.