Polyamine Induction of Secondary Metabolite Biosynthetic Genes in Fungi Is Mediated by Global Regulator LaeA and α-NAC Transcriptional Coactivator: Connection to Epigenetic Modification of Histones

Polyamines are polycationic compounds present in all living cells that exert functions at different levels in the metabolism. They bind to DNA and RNA and modulate DNA replication and gene expression. Some of these regulatory effects are exerted by promoting condensation of nucleosomes, a mechanism closely connected with epigenetic modification by histone methylation and acetylation. The polyamines 1,3-diaminopropane and spermidine induce expression of the global regulator LaeA and increase by several folds the formation of the α-NAC transcriptional co-activator, a subunit of the nascent polypeptide-associated complex. The global regulator LaeA controls the switch from primary growth to secondary metabolite production and differentiation when an essential nutrient in the growth medium becomes limiting. α-NAC exerts significant control over the biosynthesis of secondary metabolites and fungal pathogenicity on plants. When purified α-NAC protein is added to a tomato host plant, it induces plant resistance to fungal infections and triggers the development of system-acquired resistance in other plants. Spermidine extends the life of yeast cells and prolongs the half-life of penicillin gene transcripts in Penicillium chrysogenum. This article discusses advances in the basis of understanding the mechanism of plant–fungi interaction and the effect of small fungal metabolites and epigenetic modifiers in this interaction.