Allyl-isothiocyanate treatment induces a complex transcriptional reprogramming including heat stress, oxidative stress and plant defence responses in Arabidopsis thaliana

Comparison of the transcriptional response to allyl-ITC with the CPR response. (XLSX 85 kb

Frass from yellow mealworm (Tenebrio molitor) as plant fertilizer and defense priming agent

Producción CientíficaWorld population growth requires the development of a sustainable agriculture that allows feeding all the inhabitants of the planet, while reducing the use of agrochemicals. Currently, the insect farming industry for food and feed production is developing exponentially throughout the world; also producing insect frass with a potential utilization within agriculture and greenhouse industry. In the case of the yellow mealworm (Tenebrio molitor), few studies have been developed so far on the use of frass as a fertilizer, and there are none on its ability to activate plant defenses. By applying 2% sterilized mealworm frass to tomato we found a significant increase in its growth, demonstrating that the microbiota might not play a key role in its fertilizing capacity. In addition, the application of frass to sunflowers under different situations of nutritional deficit allowed us to determine what specific nutrients this fertilizer may be providing to the plant, finding a possible deficiency in the supply of N, but with sufficient amounts of P, K, Ca, and S. With respect to the induction of defenses, mealworm insect frass did not induce local root defenses in a root callose deposition assay in Arabidopsis thaliana under our experimental conditions. However, it activated systemic defenses in Arabidopsis thaliana by inducing defense genes in the absence of pathogen, further enhanced by infection with the necrotrophic fungus Botrytis cinerea. Therefore, mealworm frass could be a good fertilizer resource and plant defense inducer to support development of sustainable agriculture.Norwegian Research Council (grant RCN 250953

The Role of a Glucosinolate-Derived Nitrile in Plant Immune Responses

Glucosinolates are defense-related secondary metabolites found in Brassicaceae. When Brassicaceae come under attack, glucosinolates are hydrolyzed into different forms of glucosinolate hydrolysis products (GHPs). Among the GHPs, isothiocyanates are the most comprehensively characterized defensive compounds, whereas the functional study of nitriles, another group of GHP, is still limited. Therefore, this study investigates whether 3-butenenitrile (3BN), a nitrile, can trigger the signaling pathways involved in the regulation of defense responses in Arabidopsis thaliana against biotic stresses. Briefly, the methodology is divided into three stages, (i) evaluate the physiological and biochemical effects of exogenous 3BN treatment on Arabidopsis, (ii) determine the metabolites involved in 3BN-mediated defense responses in Arabidopsis, and (iii) assess whether a 3BN treatment can enhance the disease tolerance of Arabidopsis against necrotrophic pathogens. As a result, a 2.5 mM 3BN treatment caused lesion formation in Arabidopsis Columbia (Col-0) plants, a process found to be modulated by nitric oxide (NO). Metabolite profiling revealed an increased production of soluble sugars, Krebs cycle associated carboxylic acids and amino acids in Arabidopsis upon a 2.5 mM 3BN treatment, presumably via NO action. Primary metabolites such as sugars and amino acids are known to be crucial components in modulating plant defense response

Glucosinolate-Derived Isothiocyanates Inhibit Arabidopsis Growth and the Potency Depends on Their Side Chain Structure

Isothiocyanates (ITCs), the biologically important glucosinolate breakdown products, can present health-promoting effects, play an important role in plant defense and affect plant cellular mechanisms. Here, we evaluated the biological effects of ITCs on Arabidopsis thaliana by assessing growth parameters after long-term exposure to low concentrations of aliphatic and aromatic ITCs, ranging from 1 to 1000 µM. Treatment with the aliphatic allylisothiocyanate (allyl-ITC) led to a significant reduction of root length and fresh weight in a dose-dependent manner and affected the formation of lateral roots. To assess the importance of a hormonal crosstalk in the allyl-ITC-mediated growth reduction, the response of auxin and ethylene mutants was investigated, but our results did not allow us to confirm a role for these hormones. Aromatic ITCs generally led to a more severe growth inhibition than the aliphatic allyl-ITC. Interestingly, we observed a correlation between the length of their side chain and the effect these aromatic ITCs caused on Arabidopsis thaliana, with the greatest inhibitory effect seen for 2-phenylethyl-ITC. Root growth recovered when seedlings were removed from exposure to ITCs

Arabidopsis mutants impaired in glutathione biosynthesis exhibit higher sensitivity towards the glucosinolate hydrolysis product allyl-isothiocyanate

Upon tissue damage the plant secondary metabolites glucosinolates can generate various hydrolysis products, including isothiocyanates (ITCs). Their role in plant defence against insects and pest and their potential health benefits have been well documented, but our knowledge regarding the endogenous molecular mechanisms of their effect in plants is limited. Here we investigated the effect of allyl-isothiocyanate (AITC) on Arabidopsis thaliana mutants impaired in homeostasis of the low-molecular weight thiol glutathione. We show that glutathione is important for the AITC-induced physiological responses, since mutants deficient in glutathione biosynthesis displayed a lower biomass and higher root growth inhibition than WT seedlings. These mutants were also more susceptible than WT to another ITC, sulforaphane. Sulforaphane was however more potent in inhibiting root growth than AITC. Combining AITC with the glutathione biosynthesis inhibitor L-buthionine-sulfoximine (BSO) led to an even stronger phenotype than observed for the single treatments. Furthermore, transgenic plants expressing the redox-sensitive fluorescent biomarker roGFP2 indicated more oxidative conditions during AITC treatment. Taken together, we provide genetic evidence that glutathione plays an important role in AITC-induced growth inhibition, although further studies need to be conducted to reveal the underlying mechanisms

Benzyl Cyanide Leads to Auxin-Like Effects Through the Action of Nitrilases in Arabidopsis thaliana

Plants within the Brassicales order generate glucosinolate hydrolysis products that can exert different biological effects on several organisms. Here, we evaluated the physiological effects of one of these compounds, benzyl cyanide (phenylacetonitrile), when exogenously applied on Arabidopsis thaliana. Treatment with benzyl cyanide led to a dose-dependent reduction of primary root length and total biomass. Further morphological changes like elongated hypocotyls, epinastic cotyledons, and increased formation of adventitious roots resembled a severe auxin-overproducer phenotype. The elevated auxin response was confirmed by histochemical staining and gene expression analysis of auxin-responsive genes. Nitriles are converted by specific enzymes, nitrilases (NIT1-3), to their corresponding carboxylic acids. The nitrilase mutants nit1 and nit2 tolerated benzyl cyanide treatments better than the wild type, with nit2 being less resistant than nit1. A NIT2RNAi line suppressing several nitrilases was resistant to all tested benzyl cyanide concentrations. When exposed to phenylacetic acid (PAA) – the corresponding carboxylic acid of benzyl cyanide – wild type and mutant seedlings were, however, equally susceptible and showed a more severe auxin phenotype than upon cyanide treatment. Here, we demonstrate that the auxin-like effects triggered by benzyl cyanide on Arabidopsis are due to its nitrilase-mediated conversion to the natural auxin PAA

Accumulation of Ag(I) by <i>Saccharomyces cerevisiae</i> Cells Expressing Plant Metallothioneins

The various applications of Ag(I) generated the necessity to obtain Ag(I)-accumulating organisms for the removal of surplus Ag(I) from contaminated sites or for the concentration of Ag(I) from Ag(I)-poor environments. In this study we obtained Ag(I)-accumulating cells by expressing plant metallothioneins (MTs) in the model Saccharomyces cerevisiae. The cDNAs of seven Arabidopsis thaliana MTs (AtMT1a, AtMT1c, AtMT2a, AtMT2b, AtMT3, AtMT4a and AtMT4b) and four Noccaea caerulescens MTs (NcMT1, NcMT2a, NcMT2b and NcMT3) fused to myrGFP displaying an N-terminal myristoylation sequence for plasma membrane targeting were expressed in S. cerevisiae and checked for Ag(I)-related phenotype. The transgenic yeast cells were grown in copper-deficient media to ensure the expression of the plasma membrane high-affinity Cu(I) transporter Ctr1, and also to elude the copper-related inhibition of Ag(I) transport into the cell. All plant MTs expressed in S. cerevisiae conferred Ag(I) tolerance to the yeast cells. Among them, myrGFP-NcMT3 afforded Ag(I) accumulation under high concentration (10&#8315;50 &#956;M), while myrGFP-AtMT1a conferred increased accumulation capacity under low (1 &#956;M) or even trace Ag(I) (0.02&#8315;0.05 &#956;M). The ability to tolerate high concentrations of Ag(I) coupled with accumulative characteristics and robust growth showed by some of the transgenic yeasts highlighted the potential of these strains for biotechnology applications

Assessment of oxidative stress response genes in Avicennia marina exposed to oil contamination - Polyphenol oxidase (PPOA) as biomarker

Mangrove plants, which inhabit and form sensitive ecosystems in the intertidal zones of tropical and subtropical coastlines, though vulnerable to petroleum pollution, still maintain their growth under oil contamination. To elucidate the molecular response of mangrove plants to crude oil–sediment mixture, seeds of Avicennia marina were planted and grown on 0, 2.5, 5.0, 7.5 and10 % (w/w) oil-contaminated soil. Plant biomass was highly affected from 3.05 ± 0.28 (Control) to 0.50 ± .07 (10 %) and from 3.47 ± 0.12 to 1.88 ± 0.08 in 2 and 4 months old plants respectively. The expression analysis of 11genes belonging to detoxification pathways in the roots and leaves of 2 and 4 month-old plants was evaluated by qRT-PCR. Our results showed changes in expression levels of Fe-SOD, Mn-SOD, CAT, PRX, PPOs, GSTs, and NAP2 whose products are involved in reactive oxygen species (ROS) and xenobiotic detoxification. PPOA showed the highest expression induction of 43 ± 1.15, followed by CAT (12.61 ± 3.25) and PPOB (6.38 ± 1.34) in leaves of 2 months old seedlings grown on 7.5, 10 and 7.5 % oil contaminated soil respectively. PPOA (39.23 ± 2.1), PRX (32.13 ± 1.2) as well as PPOB (26.11 ± 1.3) showed the highest expression induction in leaves of 4 months old plants grown in 2.5 % oil contaminated soil. Our data indicated that PPOA can be a good biomarker candidate gene for long term exposure to oil contamination in A. marina

Accumulation of (Ag(I) by Saccharomyces cereviseae cells expressing plant metallothioneins

The various applications of Ag(I) generated the necessity to obtain Ag(I)-accumulating organisms for the removal of surplus Ag(I) from contaminated sites or for the concentration of Ag(I) from Ag(I)-poor environments. In this study we obtained Ag(I)-accumulating cells by expressing plant metallothioneins (MTs) in the model Saccharomyces cerevisiae. The cDNAs of seven Arabidopsis thaliana MTs (AtMT1a, AtMT1c, AtMT2a, AtMT2b, AtMT3, AtMT4a and AtMT4b) and four Noccaea caerulescens MTs (NcMT1, NcMT2a, NcMT2b and NcMT3) fused to myrGFP displaying an Nterminal myristoylation sequence for plasma membrane targeting were expressed in S. cerevisiae and checked for Ag(I)-related phenotype. The transgenic yeast cells were grown in copper-deficient media to ensure the expression of the plasma membrane high-affinity Cu(I) transporter Ctr1, and also to elude the copper-related inhibition of Ag(I) transport into the cell. All plant MTs expressed in S. cerevisiae conferred Ag(I) tolerance to the yeast cells. Among them, myrGFP-NcMT3 afforded Ag(I) accumulation under high concentration (10–50 μM), while myrGFP-AtMT1a conferred increased accumulation capacity under low (1 μM) or even trace Ag(I) (0.02–0.05 μM). The ability to tolerate high concentrations of Ag(I) coupled with accumulative characteristics and robust growth showed by some of the transgenic yeasts highlighted the potential of these strains for biotechnology applications