LOX1- and PLP1-dependent transcriptional reprogramming is essential for injury-induced conidiophore development in a filamentous fungus

Abstract

ABSTRACT Fungi use oxylipins (oxidized lipids) as signaling molecules to induce asexual development. These molecules play an essential role in the response to wounding, exerting a protective effect against plant pathogens, and are part of the inflammatory process in animals. However, the physiological and molecular mechanisms triggered by oxylipins that lead to asexual development in fungi are not well understood. Using a genetic approach, mass spectrometry, and phenotypic analysis, we describe the functional role of a patatin-like phospholipase ( plp1 ) and a unique lipoxygenase ( lox1 ) in the response to injury in the model fungus Trichoderma atroviride. lox1 and plp1 are co-expressed and regulated by damage signaling and sensing components. Phenotypic analysis revealed an essential defect in the emergence of aerial hyphae in the lox1 and plp1 null mutant strains, blocking injury-induced conidiation. In addition, functional loss analysis demonstrated that both genes are essential for wound-associated linoleic acid-derived oxylipin 13-hydroxy-9Z,11E-octadecadienoic acid (13-HODE) production and the transcriptional reprogramming required for conidiation. T. atroviride requires LOX1 and PLP1 to induce transcription factors involved in asexual development such as brlA , hox2 , and azf1 homologs at the early stages of the response and at a later stage to activate lipid metabolism and the structural proteins involved in aerial mycelium emergence. Our study shows how the cooperative function of lox1 and plp1 , during the response to wounding, regulates the molecular and physiological processes of damaged-sensitized cells that lead to reproductive aerial mycelium development and consequently, ensure survival through asexual reproduction. IMPORTANCE In addition to being considered a biocontrol agent, the fungus Trichoderma atroviride is a relevant model for studying mechanisms of response to injury conserved in plants and animals that opens a new landscape in relation to regeneration and cell differentiation mechanisms. Here, we reveal the co-functionality of a lipoxygenase and a patatin-like phospholipase co-expressed in response to wounding in fungi. This pair of enzymes produces oxidized lipids that can function as signaling molecules or oxidative stress signals that, in ascomycetes, induce asexual development. Furthermore, we determined that both genes participate in the regulation of the synthesis of 13-HODE and the establishment of the physiological responses necessary for the formation of reproductive aerial mycelium ultimately leading to asexual development. Our results suggest an injury-induced pathway to produce oxylipins and uncovered physiological mechanisms regulated by LOX1 and PLP1 to induce conidiation, opening new hypotheses for the novo regeneration mechanisms of filamentous fungi.