Nitric oxide mediates the fungal-elicitor-enhanced biosynthesis of antioxidant polyphenols in submerged cultures of Inonotus obliquus

Abstract

A fungal elicitor prepared from the cell debris of the plant-pathogenic ascomycete Alternaria alternata induces multiple responses by Inonotus obliquus cells, including an increase in generation of nitric oxide (NO), activity of phenylalanine ammonia lyase (PAL) and accumulation of total mycelial phenolic compounds (TMP), but does not trigger production of oxylipins or jasmonic acid (JA). The role of NO in TMP production was investigated via the effects of the NO-specific scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPITO) and the nitric oxide synthase (NOS) inhibitor aminoguanidine (AG). TMP profiles were assayed using 1 H NMR spectroscopy combining multivariate pattern recognition strategies. Pretreatment of I. obliquus mycelia with cPITO or AG suppressed not only elicitor-enhanced NO generation and PAL activity, but also the elicitor-induced increase in TMP production. This TMP reduction by either a NO scavenger or a NOS inhibitor was reversed by exogenous addition of either a NO donor, sodium nitroprusside, or JA separately. NMR-based metabonomic analysis of TMP profiles showed that the induced TMP were hispidin analogues including inoscavins, phelligridins, davallialactone and methyldavallialactone, which possess high antioxidant activities. Thus, NO mediates an elicitor-induced increase in production of antioxidant polyphenols in I. obliquus via a signalling pathway independent of oxylipins or JA, a mechanism which differs from those in some higher plants.

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

“…S1A in the Supplementary Material) and supplemented either with 40 μg/l cell wall debris of Alternaria alternata, an elicitor for NO production (Zheng et al 2009a) or 0.1 mM NO donor sodium nitroprusside (SNP) (Sigma, St. Louis, USA), or 40 mM aminoguanidine (AG) (Sigma, St. Louis, USA), the selective inhibitor for nitric oxide synthase. The growth of mycelia (three replicates for each combination) was observed by comparing the area colonized by each fungus along the antagonism front.…”

“…Evidences have shown that NO plays a fundamental role as a signaling molecule regulating normal physiological processes in animal cells and acts as a key player in the regulation of different plant developmental processes (Gas et al 2009;Yu et al 2014). Previously, we have found that increased NO pools resulted in higher accumulation of styrylpyrone polyphenols in I. obliquus (Zheng et al 2009a).…”

“…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.…”

Involvement of NADPH oxidase-mediated H2O2 signaling in PB90-induced hypericin accumulation in Hypericum perforatum cells

“…Therefore, the use of elicitors from microorganisms has been considered to be one of the most effective strategies for improving the productivity of useful secondary metabolites in plant cell cultures (Ciddi et al 1995;Ramani and Chelliah 2007;Xu et al 2005;Zheng et al 2009). In order to examine the effect of PB90 on secondary metabolite production of cultured plant cells, we determined hypericin production of Hypericum perforatum L. cells treated with PB90.…”

The regulatory mechanism of fungal elicitor-induced secondary metabolite biosynthesis in medical plants

“…This declared NO plays a regulatory role in the upstream of JA signaling pathway . However, NO is not fully dependent on JA signaling pathway as NO also mediates an elicitor-induced increase in production of antioxidant polyphenols in L obliquus via a signaling pathway independent of oxylipins or JA, a mechanism which differs from those in some higher plants (Zheng et al 2009). Whether these pathways are JA-dependent or not, which may depend on the plant species.…”