Fungal and algal gene expression in early developmental stages of lichen-symbiosis

Abstract

How plants and microbes recognize each other and interact to form long-lasting relationships remains one of the central questions in cellular communication. The symbiosis between the filamentous fungus Cladonia grayi and the single-celled green alga Asterochloris sp. was used to determine fungal and algal genes upregulated in vitro in early lichen development. cDNA libraries of upregulated genes were created with suppression subtractive hybridization in the first two stages of lichen development. Quantitative PCR subsequently was used to verify the expression level of 41 and 33 candidate fungal and algal genes respectively. Induced fungal genes showed significant matches to genes putatively encoding proteins involved in self and non-self recognition, lipid metabolism, and negative regulation of glucose repressible genes, as well as to a putative d-arabitol reductase and two dioxygenases. Upregulated algal genes included a chitinase-like protein, an amino acid metabolism protein, a dynein-related protein and a protein arginine methyltransferase. These results also provided the first evidence that extracellular communication without cellular contact can occur between lichen symbionts. Many genes showing slight variation in expression appear to direct the development of the lichen symbiosis. The results of this study highlight future avenues of investigation into the molecular biology of lichen symbiosis.

Advanced methods for the study of the chemistry and the metabolism of lichens

“…Differential expression of different gene families like heat shock proteins, glutathione-Stransferases and ABC transporters could be shown as response to Cd exposure. Joneson et al (2011) focussed on changes in gene expression during relichenization of the symbionts of Cladonia grayi finding an unexpected wealth of candidate genes. For some of these, like a lipase and a chitinase, differential expression could be verified between the symbiotic and aposymbiotic phase, but further studies are clearly necessary.…”

Genomic insights into the mitochondria of 11 eastern North American species of Cladonia

“…Cladonia grayi; Joneson et al 2011). Here, we present annotated mitochondrial genomes of nine species of Cladonia: C. apodocarpa, C. caroliniana, C. furcata, C. leporina, C. petrophila, C. peziziformis, C. robbinsii, C. stipitata, and C. subtenuis.…”

Endolichenic fungi: the lesser known fungal associates of lichens

“…Endophyte infection upregulates numerous defence-related genes in the plant host (Mejía et al 2014). Although it is known that during the early stage of interaction between the mycobiont and the photobiont in a lichen, several genes in both the partners are upregulated (Joneson et al 2011), it is yet to be ascertained if, like the endophytes, the endolichenic fungi influence the gene regulation in their lichen hosts.…”