Co-cultivation of Curcuma longa with Piriformospora indica Enhances the Yield and Active Ingredients

The rhizome of Curcuma longa is used in the traditional medicinal system. Its secondary metabolites curcumin and the volatile oil possess wound-healing properties and inhibitory activities against certain pathogenic fungi and bacteria. Piriformospora indica is a root endophytic fungus that colonizes many plant roots and promotes the growth. P. indica was cultivated in the 5 litre capacity fermentor under standard conditions. The filtered biomass was then mixed with raw talcum powder. The propagative buds were treated with this formulation containing both sterile and inoculated fungus. We demonstrated that co- cultivation of C. longa and P. indica resulted in pronounced productivity and enhanced secondary metabolites- curcumin and volatile oil in farmers’ field. To the authors best of knowledge this is the first report where symbiotic fungus has added value to this medicinal plant in the agricultural field

Photosynthetic electron transport determines nitrate reductase gene expression and activity in higher plants

The influence of photosynthetic electron flow in chloroplasts on the expression and enzyme activity of the cytosolic nitrate reductase (NR) was studied. Using light sources that predominantly excite either photosystem I (PSI) or photosystem II (PSII), we modulated photosynthetic electron transport in tobacco, Arabidopsis, and Lemna sprouts. In all instances, oxidation of components of photosynthetic electron flow by PSI light correlated with an increase in NR activity and/or transcription. This is confirmed by experiments with electron transport inhibitors 3-(3',4'-dichlorophenyl)-1,1'-dimethyl urea and 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone. In addition, a Lemna mutant deficient in the cytochrome b6/f complex failed to respond to the different light sources and exhibited a constitutively high level of NR activity. These data indicate that NR is activated by the oxidized state of an electron transport component located after the plastoquinone pool. An involvement of the cytoplasmic photoreceptor phytochrome A in this light regulation could be excluded, since anArabidopsis phytochrome A mutant exhibited a wild-type like response. The observation that NR activity in the cytoplasm and the expression of its gene in the nucleus is controlled by signals from photosynthetic electron flow adds a new facet to the intracellular cross-talk between chloroplasts and the nucleus

Microarray analyses during early and later stages of the Arabidopsis/Piriformospora indica interaction

Colonization of the roots of different plant species by Piriformospora indica results in better plant performance and biotic and abiotic stress tolerance. An increase of the biomass and seed yield is other beneficial effect of P. indica for the host plants. The interaction of P. indica with Arabidopsis thaliana roots is a unique model system to study symbiotic relationships. We describe a co-cultivation system which allows us to investigate the effects of fungal exudates on the root transcriptome before and after the establishment of a physical contact, and during early phases of root colonization. We present a detailed protocol which facilitates easy reproduction of the results (NCBI GEO accession number GSE58771) published by Vahabi et al. (2015) in BMC Plant Biology [1]

Indole-3-acetaldoxime derived compounds restrict root colonization in the beneficial interaction between <em>Arabidopsis</em> roots and the endophyte <em>Piriformospora indica</em>

The growth-promoting and root-colonizing endophyte Piriformospora indica induces camalexin and the expression of CYP79B2, CYP79B3, CYP71A13, PAD3, and WRKY33 required for the synthesis of indole-3-acetaldoxime (IAOx)-derived compounds in the roots of Arabidopsis seedlings. Upregulation of the mRNA levels by P. indica requires cytoplasmic calcium elevation and mitogen-activated protein kinase 3 but not root-hair-deficient 2, radical oxygen production, or the 3-phosphoinositide-dependent kinase 1/oxidative signal-inducible 1 pathway. Because P. indica–mediated growth promotion is impaired in cyp79B2 cyp79B3 seedlings, while pad3 seedlings—which do not accumulate camalexin—still respond to the fungus, IAOx-derived compounds other than camalexin (e.g., indole glucosinolates) are required during early phases of the beneficial interaction. The roots of cyp79B2 cyp79B3 seedlings are more colonized than wild-type roots, and upregulation of the defense genes pathogenesis-related (PR)-1, PR-3, PDF1.2, phenylalanine ammonia lyase, and germin indicates that the mutant responds to the lack of IAOx-derived compounds by activating other defense processes. After 6 weeks on soil, defense genes are no longer upregulated in wild-type, cyp79B2 cyp79B3, and pad3 roots. This results in uncontrolled fungal growth in the mutant roots and reduced performance of the mutants. We propose that a long-term harmony between the two symbionts requires restriction of root colonization by IAOx-derived compounds

Piriformospora indica Reprograms Gene Expression in Arabidopsis Phosphate Metabolism Mutants But Does Not Compensate for Phosphate Limitation

Piriformospora indica is an endophytic fungus of Sebacinaceae which colonizes the roots of many plant species and confers benefits to the hosts. We demonstrate that approximately 75% of the genes, which respond to P. indica in Arabidopsis roots, differ among seedlings grown on normal phosphate (Pi) or Pi limitation conditions, and among wild-type and the wrky6 mutant impaired in the regulation of the Pi metabolism. Mapman analyses suggest that the fungus activates different signaling, transport, metabolic and developmental programs in the roots of wild-type and wrky6 seedlings under normal and low Pi conditions. Under low Pi, P. indica promotes growth and Pi uptake of wild-type seedlings, and the stimulatory effects are identical for mutants impaired in the PHOSPHATE TRANSPORTERS1;1, -1;2 and -1;4. The data suggest that the fungus does not stimulate Pi uptake, but adapts the expression profiles to Pi limitation in Pi metabolism mutants

The OXI1 Kinase Pathway Mediates<em> Piriformospora</em> indica-Induced Growth Promotion in Arabidopsis

International audiencePiriformospora indica is an endophytic fungus that colonizes roots of many plant species and promotes growth and resistance to certain plant pathogens. Despite its potential use in agriculture, little is known on the molecular basis of this beneficial plant-fungal interaction. In a genetic screen for plants, which do not show a P. indica-induced growth response, we isolated an Arabidopsis mutant in the OXI1 (Oxidative Signal Inducible1) gene. OXI1 has been characterized as a protein kinase which plays a role in pathogen response and is regulated by H(2)O(2) and PDK1 (3-PHOSPHOINOSITIDE-DEPENDENT PROTEIN KINASE1). A genetic analysis showed that double mutants of the two closely related PDK1.1 and PDK1.2 genes are defective in the growth response to P. indica. While OXI1 and PDK1 gene expression is upregulated in P. indica-colonized roots, defense genes are downregulated, indicating that the fungus suppresses plant defense reactions. PDK1 is activated by phosphatidic acid (PA) and P. indica triggers PA synthesis in Arabidopsis plants. Under beneficial co-cultivation conditions, H(2)O(2) formation is even reduced by the fungus. Importantly, phospholipase D (PLD)alpha 1 or PLD delta mutants, which are impaired in PA synthesis do not show growth promotion in response to fungal infection. These data establish that the P. indica-stimulated growth response is mediated by a pathway consisting of the PLD-PDK1-OXI1 cascade