Priority effects are receiving renewed interest in microbial ecology, but their underlying molecular mechanisms remain poorly understood. Our recent work shows that priority effects can increase community diversity of nectar-inhabiting microbes, and we previously isolated and genome-resequenced 102 isolates of a cosmopolitan nectar yeast, Metschnikowia reukaufii, collected from nectar of the monkey flower, Diplacus aurantiacus, in and around the San Francisco Peninsula of California. To investigate the molecular basis of observed priority effects, we compared contribution of population-level variation in the transcriptional and metabolic responses to an early colonization of nectar by M. rancensis, another common species of nectar yeast. M. rancensis engages in differential, but strong priority effects with the 102 isolates of M. reukaufii, which form three genetically and phenotypically distinct groups. We grew M. rancensis in synthetic nectar and filtered the yeast away to simulate the chemical conditioning of nectar by M. rancensis. We then grew the 102 M. reukaufii isolates in nectar pre-conditioned by M. rancensis or non-conditioned nectar for 10 hours, after which we harvested the total RNA and the spent nectar. We identified metabolites released in the nectar using targeted metabolomics and identified significantly differentially expressed genes between isolates and treatments.
Results/Conclusions
Preliminary analysis indicates that M. reukaufii isolates differ in their transcriptional responses to conditioning by M. rancensis and that differentially expressed genes between treatments were enriched in a variety of functions, including membrane transport proteins, as evaluated using sequence homology to Saccharomyces cerevisiae. Additional analyses will include mapping expression quantitative trait loci (eQTLs) to correlate differential gene expression and small nucleotide polymorphisms (SNPs) in order to evaluate how genome-level differences influence regulation of gene expression. This multi -omics approach will inform our understanding of the role natural genotypic variation plays in molecular traits important for community assembly.