Epigenetic modifications in pathogenic filamentous fungus: a deep insight from Magnaporthe oryzae

Abstract

Epigenetic modification plays a crucial role at transcriptional and translational levels in the cell, leading to various altered functions of genes without alteration at the genetic levels. In eukaryotes, the best-studied modifications are Histone modification and DNA methylation, demethylation, acetylation, deacetylation, protein ubiquitination and sumoylation which further serves a role in activation, inhibition, or unknown functions in the various developmental stages. The involvement of epigenetic modification in the infectious growth of Magnaporthe oryzae is a largely unexplored segment. The epigenetic modification is critically regulating various developmental stages in M. oryzae e.g. MoSet1, a H3K4 methyltransferase directly or indirectly control wide range of cell wall degrading enzyme (CWDEs) and affect appressorium mediated cuticular penetration, histone deacetylases (HDACs) MoRpd3 and MoHst4 regulate conidial formation and conidial cell death, a prerequisite for the appressorial mediated fungal invasion. Chip-seq and RNA-seq in planta analysis showed a dynamic histone modification at H3K27 contribute to the fungal genome regulation specifically during infection. Deubiquitinating enzyme MoUbp14 required for stress response, nutrient utilisation, pathogenesis and MoUbp8 required for infection related development like septum formation and carbon catabolite repression in M. oryzae. A well organised small ubiquitin like modifier (SUMO) pathways (including MoSmt3, MoAos1, MoUba2, MoUbc9) play key roles in colony growth, conidia formation (four septins found to be SUMOylated), virulence and cell cycle related phenotypes in M. oryzae. The involvement of short non-coding RNA (sRNA) regulation in M. oryzae is impeccable and act as a master modulator that negatively regulate gene expression either at transcription or posttranscription level. A plethora of sRNA biogenesis pathway genes like MoDcl2, MoAgo1, MoAgo2, MoAgo3, MoRdRP2, MoRdRP3 shows a well stablished sRNA biogenesis system controlling the growth and development of the M. oryzae. Apart from fungal development regulation the interaction of sRNA between M. oryzae and rice regulate the expression of microRNA in rice to supress the immune response in rice. Autophagic cell death is an important phenomenon during appressoria maturation. M. oryzae histone acetyltransferase (HAT) Gcn5 and MoSnt2 regulates autophagy induction along with other aspect of pathogenicity like stress response, energy metabolism, cell toxicity and death via epigenetic regulation and post translational modifications. Here we provide recent advancements in our understanding of epigenetic modification and cellular biology in the pathogenic growth of M. oryzae.