Cyclooxygenases and lipoxygenases are used by the fungus Podospora anserina to repel nematodes

Abstract

We analyzse the role in inter-kingdom communication of lipoxygenase (lox) and cyclooxygenase (cox) genes in the model fungus Podospora anserina. Through chemical analysis we define the oxylipins and volatile organic compounds (VOCs)produce by wild type and mutants for cox and lox genes, We show that the COX and LOX genes are required for the production of some eight carbon VOCs. We show that COX and LOX genes are involved in the production of chemicals repelling nematodes. This role is very different from the ones previously evidenced in other fungi.

The Lipoxygenase Lox1 Is Involved in Light‐ and Injury-Response, Conidiation, and Volatile Organic Compound Biosynthesis in the Mycoparasitic Fungus Trichoderma atroviride

“…A recent study in P. anserina demonstrated a reduced to diminished production of certain VOCs and a strongly decreased ability to repel the nematode C. elegans in double-deletion mutants lacking the genes for the two Ile-group lipoxygenases encoded in the P. anserina genome (Ferrari et al, 2018). We could not see any effect of lox1 deletion on the strength and progress of the mycoparasitic attack, irrespective of the applied light regime, in our study.…”

“…T. atroviride lox1 codes for a putative iron-containing Ile-group lipoxygenase with a predicted length of 658 amino acids bearing the characteristic WRAK motif. T. atroviride Lox1 displays considerable amino acid identity with the already functionally characterized Ile-group Lox proteins of P. anserina (PaLox1, 48.8% and PaLox2, 50.9%; Ferrari et al, 2018), F. oxysporum (FOXG_04807.2, 39%; Brodhun et al, 2013) and A. fumigatus (LoxA, 40.8%;Fischer et al, 2017).…”

“…These results are in accordance with previous studies indicating that the oxygenation of linoleic-, linolenic-, or arachidonic-acid is the initial step in oxylipin biosynthesis, followed by additional steps that finally lead to a variety of oxylipins such as C8 volatiles (Kuribayashi et al, 2002;Brodhun and Feussner, 2011;Karrer and Rühl, 2019). Altered VOC emission profiles were also described for P. anserina Lox ∆ mutants which, however, still produced three C8 molecules including 1-octen-3-ol and 3-octanone, whose synthesis was hence suggested by the authors to rely on cyclooxygenase enzymes (Ferrari et al, 2018). Screening of the T. atroviride genome revealed at least two cyclooxygenases with high sequence similarity to P. anserina PaCox1 and PaCox2, which could be responsible for 1-octen-3-ol and 3-octanone biosynthesis in the presence of light in T. atroviride.…”

“…Lipoxygenases are well known to be involved in the biosynthesis of VOCs in plants (Heiden et al, 2003), but also were reported to be essential for the production of certain volatiles in P. anserina (Ferrari et al, 2018). We therefore assessed the effect of lox1 deletion on light-dependent VOC biosynthesis in T. atroviride.…”

“…Deletion of the Aflox gene resulted in a diminished quorum-sensing dependence of the balancing between conidia and sclerotia formation in Aspergillus flavus (Horowitz Brown et al, 2008). Recently, the deletion of the two Ile-group lipoxygenase-encoding genes in Podospora anserina was reported to eradicate the production of certain C7-VOCs, thereby leading to a decreased ability of the fungus to repel the nematode Caenorhabditis elegans (Ferrari et al, 2018).…”