Nitric oxide generated by the rice blast fungus Magnaporthe oryzae drives plant infection

Abstract

SummaryPlant-derived nitric oxide (NO) triggers defence, priming the onset of the hypersensitive response and restricting pathogen ingress during incompatibility. However, little is known about the role of pathogen-produced NO during pre-infection development and infection. We sought evidence for NO production by the rice blast fungus during early infection.NO production was measured using fluorescence of DAR-4M and the role of NO assessed using NO scavengers. The synthesis of NO was investigated by targeted knockout of genes potentially involved in NO synthesis, including nitric oxide synthase-like genes (NOL2 and NOL3) and nitrate (NIA1) and nitrite reductase (NII1), generating single and double Dnia1Dnii1, Dnia1Dnol3, and Dnol2Dnol3 mutants.We demonstrate that Magnaporthe oryzae generates NO during germination and in early development. Removal of NO delays germling development and reduces disease lesion numbers. NO is not generated by the candidate proteins tested, nor by other argininedependent NO systems, by polyamine oxidase activity or non-enzymatically by low pH. Furthermore, we show that, while NIA1 and NII1 are essential for nitrate assimilation, NIA1, NII1, NOL2 and NOL3 are all dispensable for pathogenicity.Development of M. oryzae and initiation of infection are critically dependent on fungal NO synthesis, but its mode of generation remains obscure.

Correlation of nitric oxide produced by an inducible nitric oxide synthase-like protein with enhanced expression of the phenylpropanoid pathway in Inonotus obliquus cocultured with Phellinus morii

“…The NOS-like proteins described in fungi represent a fungal-specific group of enzymes termed as putative biofunctional p450 reductases, each of which contains an N-terminal cytochrome p450 domain and FAD, NAD, and flavodoxin domains (Samalova et al 2013). In our study, we show that the two NOS-like proteins share a similar domain structure with those described in M. oryzae.…”

“…In higher plants, NO is generated either by NOS or nitrate/nitrite reductase depending on redox status and chemical environment (Gas et al 2009;Fr hlich and Durner 2011). Although some indications for the occurrence of NOS activity in the filamentous fungus Neurospora crassa (Ninnemann and Maier 1996) and I. obliquus Pilat (Zheng et al 2009a) have been demonstrated, the mode for NO biosynthesis remains obscure in fungi (Samalova et al 2013). In this study, we cocultured I. obliquus and Phellinus morii to examine (1) the correlation of inducible production of NO with transcription of genes encoding PAL and 4CL, and (2) the contribution of an inducible NOS-like protein (iNOSL) in NO production in fungal phenylpropanoid metabolism during fungal interspecific interactions.…”

“…, and the rice blast fungus Magnaporthe oryzae (Samalova et al 2013). The NOS-like proteins described in fungi represent a fungal-specific group of enzymes termed as putative biofunctional p450 reductases, each of which contains an N-terminal cytochrome p450 domain and FAD, NAD, and flavodoxin domains (Samalova et al 2013).…”

Investigating chitin deacetylation and chitosan hydrolysis during vegetative growth in Magnaporthe oryzae

“…Deletion of the target gene was confirmed by both PCR and Southern blot analysis, as described in Samalova et al (Samalova et al . , 2013). …”

Moving nitrogen to the centre of plant defence against pathogens

“…NO has been shown to be generated in the appressoria of Blumeria graminis and Magnaporthe oryzae to aid penetration of the host (Prats et al, 2008;Samalova et al, 2013). In the case of Phytophthora cryptogea, the virulence factor/elicitor cryptogein aids pathogenesis by promoting host cell death via NO generation (Lamotte et al, 2004).…”