Plant-parasitic-nematodes represent a major threat to the agricultural production of different crops worldwide. Due to the high toxicity of chemical nematicides, it is necessary to develop new ...control strategies against nematodes. In this respect, filamentous fungi can be an interesting biocontrol alternative. The genus Trichoderma, mycorrhizal and endophytic fungi are the main groups of filamentous fungi studied and used as biological control agents (BCAs) against nematodes as resistance inducers. They are able to reduce the damage caused by plant-parasitic nematodes directly by parasitism, antibiosis, paralysis and by the production of lytic enzymes. But they also minimize harm by space and resource-competition, by providing higher nutrient and water uptake to the plant, or by modifying the root morphology, and/or rhizosphere interactions, that constitutes an advantage for the plant-growth. Besides, filamentous fungi are able to induce resistance against nematodes by activating hormone-mediated (salicylic and jasmonic acid, strigolactones among others) plant-defense mechanisms. Additionally, the alteration of the transport of chemical defense components through the plant or the synthesis of plant secondary metabolites and different enzymes can also contribute to enhancing plant defenses. Therefore, the use of filamentous fungi of the mentioned groups as BCAs is a promising durable biocontrol strategy in agriculture against plant-parasitic nematodes.
Background Seeds host bacterial inhabitants but only a limited knowledge is available on which taxa inhabit seed, which niches could be colonized, and what the routes of colonization are. Scope ...Within this commentary, a discussion is provided on seed bacterial inhabitants, their taxa, and from where derive the seed colonizers. Conclusions Seeds/and grains host specific bacteria deriving from the anthosphere, carposphere, or from cones of gymnosperms and inner tissues of plants after a long colonization from the soil to reproductive organs.
Fungal parasitism depends on the ability to invade host organisms and mandates adaptive cell wall remodeling to avoid detection and defense reactions by the host. All plant and human pathogens share ...invasive strategies, which aid to escape the chitin-triggered and chitin-targeted host immune system. Here we describe the full spectrum of the chitin/chitosan-modifying enzymes in the mycoparasite Trichoderma atroviride with a central role in cell wall remodeling. Rapid adaption to a variety of growth conditions, environmental stresses and host defense mechanisms such as oxidative stress depend on the concerted interplay of these enzymes and, ultimately, are necessary for the success of the mycoparasitic attack. To our knowledge, we provide the first in class description of chitin and associated glycopolymer synthesis in a mycoparasite and demonstrate that they are essential for biocontrol. Eight chitin synthases, six chitin deacetylases, additional chitinolytic enzymes, including six chitosanases, transglycosylases as well as accessory proteins are involved in this intricately regulated process. Systematic and biochemical classification, phenotypic characterization and mycoparasitic confrontation assays emphasize the importance of chitin and chitosan assembly in vegetative development and biocontrol in T. atroviride. Our findings critically contribute to understanding the molecular mechanism of chitin synthesis in filamentous fungi and mycoparasites with the overarching goal to selectively exploit the discovered biocontrol strategies.
Seed-associated bacteria represent an important reservoir of microorganisms passed onto progeny plants and have been postulated to be important for early plant development and early plant vigor. ...According to a few reports, some bacterial taxa seem to be transferred from seed to seed and some seed-associated microorganisms may derive from insect visits during flowering; however, the origin of seed endophytes is poorly understood. To better understand the origin, ecology, and functional role of seed bacterial endophytes, we planted Setaria viridis seeds over several generations in a sterile growth substrate. Seed microbiota of each generation were analyzed by next generation sequencing of 16S rRNA genes and seeds were characterized regarding to their germination and plant growth. Growing plants in a sterile (or highly depleted) substrate resulted in seed microbiota, which were largely less diverse and which had altered community composition, particularly at later generations, indicating that soil is an important reservoir of seed microbiota. Some taxa were inherited to the next generations seeds; however, different subsets of taxa were inherited in different seeds/seed batches and across different generations. This suggests that other factors than the host control the establishment of most seed endophytes and only few, e.g., obligate endophytes, might be consistently inherited. Furthermore, we observed a drastic decline in seed vigor and later generations were particularly affected. Overall, our results demonstrated that the supply of endophytes from external sources such as the soil/rhizosphere environment is highly important for the build-up of a healthy seed microbiome warranting early plant establishment and vigor of next generation plants.
The association of the plant microbiota is a successional process that starts with the seed and its intrinsic microbiota. The recently reported relevance of seeds as carriers of microbiota has ...encouraged investigations of the assembly of these communities in different tissues. Here, we address the contributions of both seed and soil bacterial microbiota in the assembly of communities within endospheres of adult plants by 16S ribosomal RNA gene-based Illumina sequencing. Surface-sterilized seeds of the model plant Setaria viridis were sown in sterile conditions and seedlings were transferred onto either their native soil or a foreign soil. Soil-derived bacterial colonizers contributed to the highest portion of endophytic microbiota, with varying community composition depending on the cultivation soil. In contrast, the contribution of seed microbiota in those of adult plants was less evident. Moreover, seedlings grown in their native soils resulted in plants with consistent endophytic assemblages, whereas a dramatic increase in variability was observed for rhizosphere and endophytic root communities of plants grown in foreign soils.
The total global food demand is expected to increase up to 50% between 2010 and 2050; hence, there is a clear need to increase plant productivity with little or no damage to the environment. In this ...respect, biochar is a carbon-rich material derived from the pyrolysis of organic matter at high temperatures with a limited oxygen supply, with different physicochemical characteristics that depend on the feedstock and pyrolysis conditions. When used as a soil amendment, it has shown many positive environmental effects such as carbon sequestration, reduction of greenhouse gas emissions, and soil improvement. Biochar application has also shown huge benefits when applied to agri-systems, among them, the improvement of plant growth either in optimal conditions or under abiotic or biotic stress. Several mechanisms, such as enhancing the soil microbial diversity and thus increasing soil nutrient-cycling functions, improving soil physicochemical properties, stimulating the microbial colonization, or increasing soil P, K, or N content, have been described to exert these positive effects on plant growth, either alone or in combination with other resources. In addition, it can also improve the plant antioxidant defenses, an evident advantage for plant growth under stress conditions. Although agricultural residues are generated from a wide variety of crops, cereals account for more than half of the world’s harvested area. Yet, in this review, we will focus on biochar obtained from residues of the most common and relevant cereal crops in terms of global production (rice, wheat, maize, and barley) and in their use as recycled residues to stimulate plant growth. The harvesting and processing of these crops generate a vast number and variety of residues that could be locally recycled into valuable products such as biochar, reducing the waste management problem and accomplishing the circular economy premise. However, very scarce literature focused on the use of biochar from a crop to improve its own growth is available. Herein, we present an overview of the literature focused on this topic, compiling most of the studies and discussing the urgent need to deepen into the molecular mechanisms and pathways involved in the beneficial effects of biochar on plant productivity.
The accumulation of toxic metals and metalloids, such as cadmium (Cd), mercury (Hg), or arsenic (As), as a consequence of various anthropogenic activities, poses a serious threat to the environment ...and human health. The ability of plants to take up mineral nutrients from the soil can be exploited to develop phytoremediation technologies able to alleviate the negative impact of toxic elements in terrestrial ecosystems. However, we must select plant species or populations capable of tolerating exposure to hazardous elements. The tolerance of plant cells to toxic elements is highly dependent on glutathione (GSH) metabolism. GSH is a biothiol tripeptide that plays a fundamental dual role: first, as an antioxidant to mitigate the redox imbalance caused by toxic metal(loid) accumulation, and second as a precursor of phytochelatins (PCs), ligand peptides that limit the free ion cellular concentration of those pollutants. The sulphur assimilation pathway, synthesis of GSH, and production of PCs are tightly regulated in order to alleviate the phytotoxicity of different hazardous elements, which might induce specific stress signatures. This review provides an update on mechanisms of tolerance that depend on biothiols in plant cells exposed to toxic elements, with a particular emphasis on the Hg-triggered responses, and considering the contribution of hormones to their regulation.
•Constant light alters temporal patterns of c-Fos in the suprachiasmatic nucleus.•Chronic constant light disturbs the overt expression of activity and hormonal circadian rhythms.•Rats exposed ...chronically to constant light develop depressive like symptoms characterized by low sucrose ingestion.•Extended light at night can alter the activity of the biological clock and lead to depression.
Depression is strongly associated with the circadian system, disruption of the circadian system leads to increased propensity to disease and to mood disorders including depression. The present study explored in rats the effects of circadian disruption by constant light on behavioral and hormonal indicators of a depressive-like condition and on the biological clock, the suprachiasmatic nucleus (SCN). Exposure to constant light for 8 weeks resulted in loss of circadian patterns of spontaneous general activity, melatonin and corticosterone. Moreover these rats exhibited anhedonia in a sucrose consumption test, and increased grooming in the open-field test, which reflects an anxiety-like condition. In the SCN decreased cellular activation was observed by c-Fos immunohistochemistry. In rats exposed to constant darkness, circadian behavioral and hormonal patterns remained conserved, however mild depresive-like indicators were observed in the anhedonia test and mild anxiety-like behaviors were observed in the open field test. Data indicate that chronic conditions of LL or DD are both disruptive for the activity of the SCN leading to depression- and anxiety-like behavior. Present results point out the main role played by the biological clock and the risk of altered photoperiods on affective behavior.
In mammals, time and metabolism are tightly coupled variables; this relationship can be illustrated by numerous examples, such as the circadian variation in food intake or the circadian response to a ...glucose bolus. We review evidence that the interaction between the suprachiasmatic nucleus and the arcuate nucleus plays a key role in the execution of these functions. The nuclei are reciprocally connected via different projections, and this interaction provides an ideal anatomical framework to modify the temporal output of the hypothalamus to metabolic organs as a consequence of the feedback from the periphery. The suprachiasmatic nucleus–arcuate nucleus relationship is essential to integrate metabolic information into the circadian system and thus adapt circadian rhythms in core body temperature, locomotor activity, food intake, and circulating molecules such as glucose and corticosterone. With the rise in obesity‐associated diseases in the world population, gaining knowledge about this relationship, and the consequences of disturbing this liaison, is essential to understand the pathogenesis of obesity.
Plant-parasitic nematodes (PPNs) interact with plants in different ways, for example, through subtle feeding behavior, migrating destructively through infected tissues, or acting as virus-vectors for ...nepoviruses. They are all obligate biotrophic parasites as they derive their nutrients from living cells which they modify using pharyngeal gland secretions prior to food ingestion. Some of them can also shield themselves against plant defenses to sustain a relatively long lasting interaction while feeding. This paper is centered on cell types or organs that are newly induced in plants during PPN parasitism, including recent approaches to their study based on molecular biology combined with cell biology-histopathology. This issue has already been reviewed extensively for major PPNs (i.e., root-knot or cyst nematodes), but not for other genera (viz.
spp.). PPNs have evolved with plants and this co-evolution process has allowed the induction of new types of plant cells necessary for their parasitism. There are four basic types of feeding cells: (i) non-hypertrophied nurse cells; (ii) single giant cells; (iii) syncytia; and (iv) coenocytes. Variations in the structure of these cells within each group are also present between some genera depending on the nematode species viz.
or
. This variability of feeding sites may be related in some way to PPN life style (migratory ectoparasites, sedentary ectoparasites, migratory ecto-endoparasites, migratory endoparasites, or sedentary endoparasites). Apart from their co-evolution with plants, the response of plant cells and roots are closely related to feeding behavior, the anatomy of the nematode (mainly stylet size, which could reach different types of cells in the plant), and the secretory fluids produced in the pharyngeal glands. These secretory fluids are injected through the stylet into perforated cells where they modify plant cytoplasm prior to food removal. Some species do not produce specialized feeding sites (viz.
), but may develop a specialized modification of the root system (e.g., unspecialized root galls or a profusion of roots). This review introduces new data on cell types and plant organs stimulated by PPNs using sources varying from traditional histopathology to new holistic methodologies.
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