Phosphatidic acid produced by phospholipase D is required for hyphal cell-cell fusion and fungal-plant symbiosis

Abstract

SummaryAlthough lipid signaling has been shown to serve crucial roles in mammals and plants, little is known about this process in filamentous fungi. Here we analyse the contribution of phospholipase D (PLD) and its product phosphatidic acid (PA) in hyphal morphogenesis and growth ofEpichloë festucaeandNeurospora crassa, and in the establishment of a symbiotic interaction betweenE. festucaeandLolium perenne. Growth ofE. festucaeandN. crassaPLD deletion strains in axenic culture, and forE. festucaein association withL. perenne, were analysed by light-, confocal- and electron microscopy. Changes in PA distribution were analysed inE. festucaeusing a PA biosensor and the impact of these changes on endocytic recycling and superoxide production investigated. We found thatE. festucaePldB and theN. crassaortholog, PLA-7, are required for polarized growth, cell fusion and ascospore development, whereas PldA/PLA-8 are dispensable for these functions. Exogenous addition of PA rescues the cell-fusion phenotype inE. festucae. PldB is also crucial forE. festucaeto establish a symbiotic association withL. perenne. This study identifies a new component of the cell-cell communication and cell fusion signaling network that controls hyphal morphogenesis and growth in filamentous fungi.