Bryophytes: how to conquer an alien planet and live happily (ever after)

There are many push and pull factors that commonly drive individuals to leave their homeland. For example, escaping competition and occupying a novel habitat undoubtedly offer the advantage of new opportunities to pilgrims, but the absence of unfavorable biotic interactions can be counterbalanced by other antagonistic abiotic forces. After all, conquering an alien planet is not now nor ever was an easy task. We cannot know how many attempts and failures have punctuated the journey that led ancestral, photosynthetic organisms to leave the aquatic world and successfully establish on dry land. However, some traits developed by the ancestors of modern bryophytes that allowed them to adapt their life cycle to such a different habitat and persist there, have been undoubtedly identified

Evaluating aflatoxin gene expression in Aspergillus section Flavi

The determination of aflatoxin production ability and differentiation of aflatoxigenic strains can be assessed by monitoring the expression of one or several key genes using reverse transcription polymerase chain reaction (RT-PCR). We herein describe the methods for RNA induction, extraction, and quality determination, and the RT-PCR conditions used to evaluate the ability of a given Aspergillus strain to produce aflatoxins.info:eu-repo/semantics/publishedVersio

Sisters in structure but different in character, some benzaldehyde and cinnamaldehyde derivatives differentially tune Aspergillus flavus secondary metabolism

Great are the expectations for a new generation of antimicrobials, and strenuous are the research efforts towards the exploration of diverse molecular scaffolds—possibly of natural origin – aimed at the synthesis of new compounds against the spread of hazardous fungi. Also high but winding are the paths leading to the definition of biological targets specifically fitting the drug’s structural characteristics. The present study is addressed to inspect differential biological behaviours of cinnamaldehyde and benzaldehyde thiosemicarbazone scaffolds, exploiting the secondary metabolism of the mycotoxigenic phytopathogen Aspergillus flavus. Interestingly, owing to modifications on the parent chemical scaffold, some thiosemicarbazones displayed an increased specificity against one or more developmental processes (conidia germination, aflatoxin biosynthesis, sclerotia production) of A. flavus biology. Through the comparative analysis of results, the ligand-based screening strategy here described has allowed us to delineate which modifications are more promising for distinct purposes: from the control of mycotoxins contamination in food and feed commodities, to the environmental management of microbial pathogens, to the investigation of specific structure–activity features for new generation drug discovery

Correlation between hormonal homeostasis and morphogenic responses in Arabidopsis thaliana seedlings growing in a Cd/Cu/Zn multi-pollution context

To date, almost no information is available in roots and shoots of the model plant Arabidopsis thaliana about the hierarchic relationship between metal accumulation, phytohormone levels, and glutathione/phytochelatin content, and how this relation affects root development. For this purpose, specific concentrations of cadmium, copper and zinc, alone or in triple combination, were supplied for 12 days to in vitro growing seedlings. The accumulation of these metals was measured in roots and shoots, and a significant competition in metal uptake was observed. Microscopic analyses revealed that root morphology was affected by metal exposure, and that the levels of trans-zeatin riboside, dihydrozeatin riboside, indole-3-acetic acid, and the auxin/cytokinin ratio varied accordingly. By contrast, under metal treatments, minor modifications in gibberellic acid and abscisic acid levels occurred. RT-PCR analysis of some genes involved in auxin and cytokinin synthesis (e.g., AtNIT in roots and AtIPT in shoots) showed on average a metal up-regulated transcription. The production of thiol-peptides was induced by all the metals, alone or in combination, and the expression of the genes involved in thiol-peptide synthesis (AtGSH1, AtGSH2, AtPCS1 and AtPCS2) was not stimulated by the metals, suggesting a full post-transcriptional control. Results show that the Cd/Cu/Zn-induced changes in root morphology are caused by a hormonal unbalance, mainly governed by the auxin/cytokinin ratio

Double gamers—can modified natural regulators of higher plants act as antagonists against phytopathogens? The case of jasmonic acid derivatives

As key players in biotic stress response of plants, jasmonic acid (JA) and its derivatives cover a specific and prominent role in pathogens-mediated signaling and hence are promising candidates for a sustainable management of phytopathogenic fungi. Recently, JA directed antimicrobial effects on plant pathogens has been suggested, supporting the theory of oxylipins as double gamers in plant-pathogen interaction. Based on these premises, six derivatives (dihydrojasmone and cis-jasmone, two thiosemicarbazonic derivatives and their corresponding complexes with copper) have been evaluated against 13 fungal species affecting various economically important herbaceous and woody crops, such as cereals, grapes and horticultural crops: Phaeoacremonium minimum, Neofusicoccum parvum, Phaeomoniella chlamydospora, Fomitiporia mediterranea, Fusarium poae, F. culmorum, F. graminearum, F. oxysporum f. sp. lactucae, F. sporotrichioides, Aspergillus flavus, Rhizoctonia solani, Sclerotinia spp. and Verticillium dahliae. The biological activity of these compounds was assessed in terms of growth inhibition and, for the two mycotoxigenic species A. flavus and F. sporotrichioides, also in terms of toxin containment. As expected, the inhibitory effect of molecules greatly varied amongst both genera and species; cis-jasmone thiosemicarbazone in particular has shown the wider range of effectiveness. However, our results show that thiosemicarbazones derivatives are more effective than the parent ketones in limiting fungal growth and mycotoxins production, supporting possible applications for the control of pathogenic fungi

The aflatox® project: Approaching the development of new generation, natural‐based compounds for the containment of the mycotoxigenic phytopathogen Aspergillus flavus and aflatoxin contamination

The control of the fungal contamination on crops is considered a priority by the sanitary authorities of an increasing number of countries, and this is also due to the fact that the geographic areas interested in mycotoxin outbreaks are widening. Among the different pre‐ and post‐harvest strategies that may be applied to prevent fungal and/or aflatoxin contamination, fungicides still play a prominent role; however, despite of countless efforts, to date the problem of food and feed contamination remains unsolved, since the essential factors that affect aflatoxins production are various and hardly to handle as a whole. In this scenario, the exploitation of bioactive natural sources to obtain new agents presenting novel mechanisms of action may represent a successful strategy to minimize, at the same time, aflatoxin contamination and the use of toxic pesticides. The Aflatox® Project was aimed at the development of new‐generation inhibitors of aflatoxigenic Aspergillus spp. proliferation and toxin production, through the modification of naturally occurring molecules: a panel of 177 compounds, belonging to the thiosemicarbazones class, have been synthesized and screened for their antifungal and anti‐aflatoxigenic potential. The most effective compounds, selected as the best candidates as aflatoxin containment agents, were also evaluated in terms of cytotoxicity, genotoxicity and epi‐genotoxicity to exclude potential harmful effect on the human health, the plants on which fungi grow and the whole ecosystem

Aspergillus flavus: controllo della biosintesi di aflatossina e strategie di biocompetizione

L'aflatossina B1 è considerata una delle micotossine più pericolose per la salute dell'uomo e degli animali. La contaminazione di alimenti e mangimi che può verificarsi, a seguito dell’infezione fungina, in ogni fase del loro processo di trasformazione (dal campo alla tavola) è causa di gravi perdite economiche. Una delle strategie che attualmente è considerata tra le più promettenti nel contenere il "rischio aflatossine" consiste nell’uso della bio-competizione quale mezzo di prevenzione dell'infezione fungina delle colture in campo. Il biocontrollo realizzato tramite l’inibizione competitiva ad opera di ceppi atossigenici (afla-) di Aspergillus flavus ha dimostrato di essere un metodo efficace per il contenimento aflatossine in arachidi, mais e semi di cotone. Le popolazioni naturali di afla- sono considerate i serbatoi da cui selezionare i biocompetitori più forti; tuttavia, selezionare i ceppi migliori non è facile, sia per la scarsità di ceppi afla- efficaci che per le diverse condizioni ambientali che possono influenzare la loro efficacia in campo. Occorrono pertanto procedure “high throughput” in grado di vagliare un numero molto elevato di isolati per identificare i buoni competitori. Le prove in campo necessarie per valutare la loro efficienza una volta rilasciati nell’ambiente sono costose e laboriose, ma esperimenti di ricostruzione condotti in laboratorio possono essere utili sia per analizzare i meccanismi biologici alla base dell'efficacia dei ceppi afla- nel prevenire la biosintesi di aflatossina, sia per ottenere indicazioni preliminari sulle prestazioni degli stessi sulle colture. In questo lavoro è stata messa a punto una procedura semplice ed economica, che sfrutta fluorescenza UV-indotta della tossina, per valutare il potenziale di ceppi afla-, che colonizzano i campi di mais della pianura padana, nel ridurre l'accumulo di aflatossina; attraverso il processo di screening è stato isolato un ceppo afla- che si è dimostrato efficace nel contenere l’accumulo di aflatossina nei confronti di tutti i ceppi aflatossigenici (afla+) isolati. Il profilo genetico del buon competitore è stato caratterizzato, e la sua efficacia testata in campo nel corso di un trial di tre anni. Sono stati analizzati alcuni dei parametri che si sospetta siano coinvolti nell'efficacia della biocompetizione: i dati riportati dimostrano che sia il momento di inoculo del ceppo afla- che il rapporto tra afla- e afla+ sono cruciali. L'effetto della concentrazione dei conidi è stato invece valutato con esperimenti in micromanipolazione in cui spore singole afla- e afla+ sono state inoculate fianco a fianco sulla superficie di terreno agarizzato. La procedur, che si avvale di un lettore di fluorescenza di piastre multipozzetto, è stata utilizzata anche per valutare l'efficacia e la cinetica di azione di composti antiossidanti (o di miscele) sull'accumulo aflatossine: è stato testato l’effetto sia di composti puri (come acido α-lipoico, acido ascorbico e N-acetil-cisteina), sia di estratti vegetali (estratti organici di radici, stelo e foglia di Citrullus colocynthis), sia di estratti naturali commerciali (estratto di semi d’uva e di Ratania, Indena®). Infine, è stata dimostrata l'efficacia biocompetitiva di un ceppo naturale di Aspergillus oryzae, isolato da mais campionato in Madagascar, contro ceppi aflatossigenici di A. flavus

Potential of biocontrol agents, antioxidant compounds and natural extracts on aflatoxin containment: a simple and highthroughput procedure

Aflatoxin B1 is considered one of the most dangerous mycotoxin for humans and animals health. Moreover severe economic losses may be encountered due to its possible contamination of food and feed during each step of their transformation process (from field to table). Preventing fungal infection/ toxin contamination of crops in the field is considered the preferred strategy to cope with the “aflatoxin risk”. Biocontrol by competitive inhibition using atoxigenic (afla–) Aspergillus flavus strains has been shown to be an effective method in aflatoxin containment in peanuts, maize and cottonseed(1). Naturally occurring populations of afla– strains are considered reservoirs from which to select the strongest biocompetitors. However, the selection of biocontrol strains is not an easy task, due both to the small amount of afla– strains and to the various environmental conditions that may affect their efficacy in the field(2). High throughput procedures are therefore desirable to screen large amount of isolates in order to identify “good competitors”. Moreover, as field trials required to assess their efficiency are expensive and laborious, reconstruction experiments have been generally performed under laboratory conditions to investigate the biological mechanisms underlying the efficacy of afla– strains in preventing aflatoxin production and/or to give a preliminary indication of strain performance when released in the crops. We developed a simple and inexpensive fluorescence-based procedure that may be used: 1) to scale-up the screening process(3) and also 2) to increase knowledge on the mechanisms interfering with mycotoxin production during intraspecific competition and 3) to analyze the effect of natural and/or synthetic compounds for their possible effects on aflatoxin biosynthesis. Here we give a report of our results concerning the evaluation of the potential of afla– strains, colonizing the corn fields of the Po Valley, in reducing aflatoxin accumulation, and show some preliminary evidence that suggest the possible use of antioxidants as part of an additional strategy to contain aflatoxin contamination of food and feed commodities. Conversely the procedure may be used to uncover the presence of antioxidant agents in complex mixtures deriving from natural sources