Biosynthesis and biological function of secondary metabolites of the rice blast fungus Pyricularia oryzae

Abstract

Filamentous fungi have many secondary metabolism genes and produce a wide variety of secondary metabolites with complex and unique structures. However, the role of most secondary metabolites remains unclear. Moreover, most fungal secondary metabolism genes are silent or poorly expressed under laboratory conditions and are difficult to utilize. Pyricularia oryzae, the causal pathogen of rice blast disease, is a well-characterized plant pathogenic fungus. P. oryzae also has a large number of secondary metabolism genes and appears to be a suitable organism for analyzing secondary metabolites. However, in case of this fungus, biosynthetic genes for only four groups of secondary metabolites have been well characterized. Among two of the four groups of secondary metabolites, biosynthetic genes were identified by activating secondary metabolism. These secondary metabolites include melanin, a polyketide compound required for rice infection; tenuazonic acid, a well-known mycotoxin produced by various plant pathogenic fungi and biosynthesized by a unique non-ribosomal peptide synthetase-polyketide synthase hybrid enzyme; nectriapyrones, antibacterial polyketide compounds produced mainly by symbiotic fungi, including plant pathogens and endophytes, and pyriculols, phytotoxic polyketide compounds. This review mainly focuses on the biosynthesis and biological functions of the four groups of P. oryzae secondary metabolites.

Enhancing the Discovery of Bioactive Secondary Metabolites From Fungal Endophytes Using Chemical Elicitation and Variation of Fermentation Media

“…Fungal endophytes are prolific producers of bioactive molecules including structurally uncommon molecules and those with remarkable biological activities ( Nisa et al, 2015 ; Gupta and Shukla, 2020 ; Ortega et al, 2021 ). However, several limiting factors such as low yields of targeted compounds and weak expression of many of their biosynthetic gene clusters under standard laboratory growth conditions limits the realization of full biosynthetic potential of these microbial factories ( González-Menéndez et al, 2018 ; Motoyama et al, 2021 ). To overcome such challenges, numerous strategies, such as co-culture, chemical elicitation, variation of culture growth conditions, and genetic engineering of strains of interest among other strategies have been employed ( Baral et al, 2018 ; Kjærbølling et al, 2019 ; Gakuubi et al, 2021 ).…”

Furanoids from the Gymnadenia conopsea (Orchidaceae) seed germination supporting fungus Ceratobasidium sp. (GS2)

“…Other compounds had not been tested germination assay due to limited amounts in this report. Symbiotic fungi are able to produce a wide variety of secondary metabolites with complex and unique structures, which make an important role in plant growth and development (Motoyama et al, 2021). Theoretically, GS2 could produce metabolites to promote seed germination.…”

The hidden power of secondary metabolites in plant-fungi interactions and sustainable phytoremediation

“…For example, the pathogenesis of Pyricularia oryzae , which cause rice blast disease, is dependent on the accumulation of fungal melanin as an SM. However, tenuazonic acid, a hybrid non-ribosomal peptide synthetase (NRP)/PKS mycotoxin, nectriapyrones, phytotoxic polyketide compounds, and pyriculols do not play significant roles ( Motoyama et al., 2021 ). Many fungal SM clusters cannot be created in a laboratory setting due to the inability to replicate the specific environmental conditions that typically induce synthesis in nature.…”