Molecular characterization of lichen growth properties on rock substrates

Abstract

This project examined lichen growth properties during nutrient starvation utilizing molecular phylogenetics. It was hypothesized that the inner portion of a lichen would be experiencing nutrient starvation and a diauxic shift versus the nutrient rich segment on the outer rim. Other Ascomycetes such as Saccharomyces show a distinct gene regulatory pattern in which mitochondrial oxidative phosphorylation enzymes are upregulated in response to glucose depletion. There is minimal genomic information for the lichen fungal genus Parmelia that grow on rock substrates in New England. Therefore, in order to study lichen gene expression, online database mining and DNA analysis was required to identify Parmelia gene sequences using homologous sequences from related Ascomycetes organisms. Degenerate DNA oligonucleotide sequences that matched conserved regions of fungal genes were used to design PCR primers for specific lichen fungal genes. After collecting local lichen populations, RNA was extracted, cDNAs were synthesized and real time PCR techniques were employed. The data showed a sharp increase in ATP1 synthase and tubulin gene expression from the outer to the inner samples, two fold and three fold respectively. Therefore, starved lichens from the inner section of the organism growing on a rock substrate undergo a diauxic shift and alter its gene expression profile. Thus, this lichen experiment determined ATP1 synthase and tubulin genes show the same upregulation in the fungal lichen species such as that which occurs in Saccharomyces. Supported by BRIN/INBRE Grant # P20 RR016457 from the NIH.