Leaf-cutting ant fungi produce cell wall degrading pectinase complexes reminiscent of phytopathogenic fungi

<p>Abstract</p> <p>Background</p> <p>Leaf-cutting (attine) ants use their own fecal material to manure fungus gardens, which consist of leaf material overgrown by hyphal threads of the basidiomycete fungus <it>Leucocoprinus gongylophorus </it>that lives in symbiosis with the ants. Previous studies have suggested that the fecal droplets contain proteins that are produced by the fungal symbiont to pass unharmed through the digestive system of the ants, so they can enhance new fungus garden growth.</p> <p>Results</p> <p>We tested this hypothesis by using proteomics methods to determine the gene sequences of fecal proteins in <it>Acromyrmex echinatior </it>leaf-cutting ants. Seven (21%) of the 33 identified proteins were pectinolytic enzymes that originated from the fungal symbiont and which were still active in the fecal droplets produced by the ants. We show that these enzymes are found in the fecal material only when the ants had access to fungus garden food, and we used quantitative polymerase chain reaction analysis to show that the expression of six of these enzyme genes was substantially upregulated in the fungal gongylidia. These unique structures serve as food for the ants and are produced only by the evolutionarily advanced garden symbionts of higher attine ants, but not by the fungi reared by the basal lineages of this ant clade.</p> <p>Conclusions</p> <p>Pectinolytic enzymes produced in the gongylidia of the fungal symbiont are ingested but not digested by <it>Acromyrmex </it>leaf-cutting ants so that they end up in the fecal fluid and become mixed with new garden substrate. Substantial quantities of pectinolytic enzymes are typically found in pathogenic fungi that attack live plant tissue, where they are known to breach the cell walls to allow the fungal mycelium access to the cell contents. As the leaf-cutting ant symbionts are derived from fungal clades that decompose dead plant material, our results suggest that their pectinolytic enzymes represent secondarily evolved adaptations that are convergent to those normally found in phytopathogens.</p

Improved enzyme production by co-cultivation of Aspergillus niger and Aspergillus oryzae and with other fungi

Aspergillus niger and Aspergillus oryzae were co-cultivated with each other and with Magnaporthe grisea or Phanerochaete chrysosporium, respectively. Enzyme assays for plant polysaccharide and lignin-degrading enzymes showed that co-cultivation can improve extracellular enzyme production. Highest β-glucosidase, α-cellobiohydrolase, β-galactosidase, and laccase activities were found for A. oryzae in combination with other fungi, in particular with P. chrysosporium. Highest β-xylosidase activity was obtained when A. niger was co-cultivated with P. chrysosporium. SDS-PAGE protein profiles demonstrated that A. niger and A. oryzae contributed most to the overall enzyme activities found in the culture medium of the mixed cultivations. These data demonstrate that co-cultivation of two major industrial fungi, A. niger and A. oryzae, results in improved production of biotechnologically relevant enzymes. © 2010 Elsevier Ltd.link_to_subscribed_fulltex

Loss of function of the carbon catabolite repressor CreA leads to low but inducer‐independent expression from the feruloyl esterase B promoter in Aspergillus niger

OBJECTIVE: With the aim to decipher the mechanisms involved in the transcriptional regulation of feruloyl esterase encoded by faeB, a genetic screen was performed to isolate A. niger mutants displaying inducer-independent expression from the faeB promoter. RESULT: PfaeB-amdS and PfaeB-lux dual reporter strains were constructed and used to isolate trans-acting mutants in which the expression of both reporters was increased, based on the ability to grow on acetamide plates and higher luciferase activity, respectively. The genetic screen on the non-inducing carbon source D-fructose yielded in total 111 trans-acting mutants. The genome of one of the mutants was sequenced and revealed several SNPs, including a point mutation in the creA gene encoding a transcription factor known to be involved in carbon catabolite repression. Subsequently, all mutants were analyzed for defects in carbon catabolite repression by determining sensitivity towards allyl alcohol. All except four of the 111 mutants were sensitive to allyl alcohol, indicating that the vast majority of the mutants are defective in carbon catabolite repression. The creA gene of 32 allyl alcohol sensitive mutants was sequenced and 27 of them indeed contained a mutation in the creA gene. Targeted deletion of creA in the reporter strain confirmed that the loss of CreA results in constitutive expression from the faeB promoter. CONCLUSION: Loss of function of CreA leads to low but inducer-independent expression from the faeB promoter in A. niger. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10529-021-03104-2