The role of glycerol in the pathogenic lifestyle of the rice blast fungus Magnaporthe oryzae

Abstract

SummaryThe rice blast fungus Magnaporthe oryzae elaborates a specialized cell called an appressorium, which is used to breach the tough outer cuticle of a rice leaf, enabling the fungus entry to host plant cells. The appressorium generates enormous turgor by accumulating glycerol to very high concentrations within the cell. Glycerol accumulation and melanization of the appressorium cell wall collectively drive turgormediated penetration of the rice leaf. In this review, we discuss the potential metabolic sources of glycerol in the rice blast fungus and how appressorium turgor is focused as physical force at the base of the infection cell, leading to the formation of a rigid penetration peg. We review recent studies of M. oryzae and other relevant appressorium-forming fungi which shed light on how glycerol is synthesized and how appressorium turgor is regulated. Finally, we provide some questions to guide avenues of future research that will be important in fully understanding the role of glycerol in rice blast disease.

Histological and ultrastructural characterization of the leaf infection events of Colletotrichum fructicola on Malus domestica ‘Gala’

“…Additionally, in the appressoria of C. fructicola , a vacuole nearly filled the cell. The vacuole of appressoria as a central element of the lytic system takes up lipid droplets to generate glycerol, contributing to appressorium turgor generation (Foster et al , ). In this study, the appressorial cone pad was close to the vacuole, which could protect the appressorial vacuole from being pierced by the appressorial cone.…”

Threonine synthase CoTHR4 is involved in infection-related morphogenesis during the pre-penetration stage in Colletotrichum orbiculare

“…Cytological observations showed that appressoria of the cothr4 mutant induced by exogenously supplied threonine exhibited a reduction in turgor generation. In C. orbiculare and M. oryzae , the melanin layer in the appressorial cell wall is a semipermeable membrane that blocks the efflux of glycerol from the appressorium, leading to high turgor pressure [47, 48]. We noticed that melanization in appressoria of the cothr4 mutant induced by exogenously supplied threonine was slightly weaker than that in the wild-type (Fig 4).…”

When green and red mycology meet: Impressions from an interdisciplinary forum on virulence mechanisms of phyto- and human-pathogenic fungi

“…62 Accordingly, several aspects of fungal cell biology that are relevant in the context of infection were addressed in the final IFoFun-2016 session that was hosted by Frank Ebel from Munich, Germany. Lauren Ryder from Exeter, UK, focused on turgor pressure modulation of the rice blast fungus Magnaporthe oryzae 63 by an osmosensing histidine kinase that supports pathogenicity but also acts as negative regulator of melanin synthesis. Holger Deising from Halle, Germany, presented data on evasion of the model pathogen Colletotrichum graminicola from plant PAMPtriggered immunity by surface modulations in biotrophic hyphae 64 and how to use host-induced silencing of essential fungal genes to improve plant health.…”