OOS 10-7
Genetic basis of local adaptations in the South African shrub Protea repens
Local adaptations leading to functional trait evolution can arise in response to environmental gradients across a species’ range. Protea repens, a widespread shrub in the highly diverse fynbos shrubland of the Greater Cape Floristic Region of South Africa, displays diverse phenotypes potentially shaped by strong environmental gradients in aridity, elevation and precipitation seasonality. This phenotypic variation harbors a great potential for revealing the genetic basis of local adaptations. In this study, we investigate if the phenotypic variation in Protea repens is shaped by the environment and we aim to reveal and quantify genetic variation among populations corresponding to these local adaptations. For this purpose, seeds were collected from nineteen populations covering most of the species geographic and climatic range, then planted in a common garden. Several leaf-related traits were measured and additionally, leaf tissues were collected for population level sequencing of transcriptomes. Our initial analysis focuses on two of these populations, inhabiting sites with strongly contrasting annual precipitation levels, which were used for transcriptome-wide differential gene expression analysis in order to identify genes and pathways associated with local adaptations. We also identified orthologs of genes that are known to be enhancing drought tolerance in Arabidopsis, expressed in leaf tissues of eight P. repens populations.
Results/Conclusions
We found strong correlations between some traits and environmental gradients: for example growth rate is strongly associated with source-site elevation, and leaf morphology with source-site precipitation patterns. Preliminary analysis of the differentially regulated genes between two populations with different precipitation levels shows enrichment in several gene ontology categories including response to water deprivation (GO:0009414; p-value=6.62E-3) and heat (GO:0009408; p-value=3.07E-5). We also found an Arabidopsis gene, Abscisic Acid Responsive element-binding Factor2, known to be important in drought tolerance to be highly expressed in all the eight populations analyzed so far. These results indicate that, regardless of the common environment plants were grown in, Protea repens displays not only global but also population specific patterns of gene regulation, which would potentially be reflected in their adaptive mechanisms to their local environments. We are now extending the analysis to all the populations and analyzing the genetic variation both in expression and sequence level and investigating their relationship to the trait data, which will give a better understanding of the mechanisms shaping these local adaptations.