Colonization of Trichoderma viride Tv-1511 in peppermint (Mentha × piperita L.) roots promotes essential oil production by triggering ROS-mediated MAPK activation

Enhanced resistance to heat and fungal infection in transgenic Trichoderma via over-expressing the HSP70 gene

Heat stress is one of the major abiotic stresses affecting the growth, sporulation, colonization and survival of Trichoderma viride. This study aimed to gain a better insight into the underlying mechanism governing the heat stress response of T. viride Tv-1511. We analysed the transcriptomic changes of Tv-1511 under normal and heat stress conditions using RNA sequencing. We observed that Tv-1511 regulates the biosynthesis of secondary metabolites through a complex network of signalling pathways. Additionally, it significantly activates the anti-oxidant defence system, heat shock proteins and stress-response-related transcription factors in response to heat stress. TvHSP70 was identified as a key gene, and transgenic Tv-1511 overexpressing TvHSP70 (TvHSP70-OE) was generated. We conducted an integrated morphological, physiological and molecular analyses of the TvHSP70-OE and wild-type strains. We observed that TvHSP70 over-expression significantly triggered the growth, anti-oxidant capacity, anti-fungal activity and growth-promoting ability of Tv-1511. Regarding anti-oxidant capacity, TvHSP70 primarily up-regulated genes involved in enzymatic and non-enzymatic anti-oxidant systems. In terms of anti-fungal activity, TvHSP70 primarily activated genes involved in the synthesis of enediyne, anti-fungal and aminoglycoside antibiotics. This study provides a comparative analysis of the functional significance and molecular mechanisms of HSP70 in Trichoderma. These findings provide a valuable foundation for further analyses.

Evolution of reactive oxygen species cellular targets for plant development

Reactive oxygen species (ROS) are the key players in regulating developmental processes of plants. Plants have evolved a large array of gene families to facilitate the ROS-regulated developmental process in roots and leaves. However, the cellular targets of ROS during plant evolutionary development are still elusive. Here, we found early evolution and large expansions of protein families such as mitogen-activated protein kinases (MAPK) in the evolutionarily important plant lineages. We review the recent advances in interactions among ROS, phytohormones, gasotransmitters, and protein kinases. We propose that these signaling molecules act in concert to maintain cellular ROS homeostasis in developmental processes of root and leaf to ensure the fine-tuning of plant growth for better adaptation to the changing climate.

Enhancement of Essential Oil Production and Expression of Some Menthol Biosynthesis-Related Genes in Mentha piperita Using Cyanobacteria

Background

Mentha piperita L. is one of the most important aromatic crops and is cultivated worldwide for essential oils (EOs).

Objectives

The aim of the present study was to investigate the potential of two cyanobacteria, Anabaena vaginicola ISB42 and Nostoc spongiaeforme var. tenue ISB65, as biological-elicitors to improve the growth and essential oil production of M. piperita.

Materials and Methods

In this experiment, inoculation of M. piperita with cyanobacteria was performed by adding 1% cyanobacterial suspension to the soil of treated pots on the first time of planting and every 20 days thereafter. The experiment was performed in a randomized complete block design in an experimental greenhouse condition. After 90 days planting, the vegetative growth factors, the content of photosynthetic pigments, as well as the quantity and quality of EOs of treated and control plants were evaluated. Also, quantitative changes in the expression of some menthol biosynthesis-related genes were investigated.

Results

Cyanobacterial application led to significant increases in M. piperita growth indices including root and shoot biomass, leaf number, leaf area, node number and ramification, as well as photosynthetic pigments content. The statistical analysis showed a 41-75 % increase in some of these growth indices, especially in Nostoc-treated plants. A. vaginicola and N. spongiaeforme var. tenue inoculation led to a 13% and 25% increase in the EOs content of M. piperita, respectively. The EOs components were also affected by cyanobacterial treatments. According to the statistical analysis, Nostoc-treated plants showed the highest amount of (-)-menthone and (-)-limonene, with a 2.36 and 1.87-fold increase compared to the control. A. vaginicola and N. spongiaeforme var. tenue inoculation also led to 40% and 98% increase in transcript level of (-)-limonene synthase gene, respectively. The expression of the (-)-menthone reductase gene, was also increased by 65% and 55% in response to A. vaginicola and N. spongiaeforme var. tenue application, respectively.

Conclusions

Our data demonstrated that in addition to growth enhancement, these two heterocystous cyanobacteria improved the quantity and quality of EOs by up-regulating the key genes involved in the menthol biosynthetic pathway. Based on our results, these cyanobacteria can be considered valuable candidates in the formulation of low-cost and environmentally friendly biofertilizers in sustainable peppermint production.

Trichoderma as a biological control agent: mechanisms of action, benefits for crops and development of formulations

Currently, the food and economic losses generated by the attack of phytopathogens on the agricultural sector constitute a severe problem. Conventional crop protection techniques based on the application of synthetic pesticides to combat these undesirable microorganisms have also begun to represent an inconvenience since the excessive use of these substances is associated with contamination problems and severe damage to the health of farmers, consumers, and communities surrounding the fields, as well as the generation of resistance by the phytopathogens to be combated. Using biocontrol agents such as Trichoderma to mitigate the attack of phytopathogens represents an alternative to synthetic pesticides, safe for health and the environment. This work explains the mechanisms of action through which Trichoderma exerts biological control, some of the beneficial aspects that it confers to the development of crops through its symbiotic interaction with plants, and the bioremedial effects that it presents in fields contaminated by synthetic pesticides. Also, detail the production of spore-based biopesticides through fermentation processes and formulation development.

Trichoderma Species: Our Best Fungal Allies in the Biocontrol of Plant Diseases-A Review

Biocontrol agents (BCA) have been an important tool in agriculture to prevent crop losses due to plant pathogens infections and to increase plant food production globally, diminishing the necessity for chemical pesticides and fertilizers and offering a more sustainable and environmentally friendly option. Fungi from the genus Trichoderma are among the most used and studied microorganisms as BCA due to the variety of biocontrol traits, such as parasitism, antibiosis, secondary metabolites (SM) production, and plant defense system induction. Several Trichoderma species are well-known mycoparasites. However, some of those species can antagonize other organisms such as nematodes and plant pests, making this fungus a very versatile BCA. Trichoderma has been used in agriculture as part of innovative bioformulations, either just Trichoderma species or in combination with other plant-beneficial microbes, such as plant growth-promoting bacteria (PGPB). Here, we review the most recent literature regarding the biocontrol studies about six of the most used Trichoderma species, T. atroviride, T. harzianum, T. asperellum, T. virens, T. longibrachiatum, and T. viride, highlighting their biocontrol traits and the use of these fungal genera in Trichoderma-based formulations to control or prevent plant diseases, and their importance as a substitute for chemical pesticides and fertilizers.

Dual inoculation of dark septate endophytes and Trichoderma viride drives plant performance and rhizosphere microbiome adaptations of Astragalus mongholicus to drought

Rhizosphere microbiome adapts their structural compositions to water scarcity and have the potential to mitigate drought stress of plants. To unlock this potential, it is crucial to understand community responses to drought in the interplay between soil properties, water management and exogenous microbes interference. Inoculation with dark septate endophytes (DSE) (Acrocalymma vagum, Paraboeremia putaminum) and Trichoderma viride on Astragalus mongholicus grown in the non‐sterile soil was exposed to drought. Rhizosphere microbiome were assessed by Illumina MiSeq sequencing of the 16S and ITS2 rRNA genes. Inoculation positively affected plant growth depending on DSE species and water regime. Ascomycota, Proteobacteria, Actinobacteria, Chloroflexi and Firmicutes were the dominant phyla. The effects of dual inoculation on bacterial community were greater than those on fungal community, and combination of P. putaminum and T. viride exerted a stronger impact on the microbiome under drought stress. The observed changes in soil factors caused by inoculation could be explained by the variations in microbiome composition. Rhizosphere microbiome mediated by inoculation exhibited distinct preferences for various growth parameters. These findings suggest that dual inoculation of DSE and T. viride enriched beneficial microbiota, altered soil nutrient status and might contribute to enhance the cultivation of medicinal plants in dryland agriculture.

The inhibitory effect of (-)-Epicatechin gallate on the proliferation and migration of vascular smooth muscle cells weakens and stabilizes atherosclerosis

Vascular smooth muscle cells (VSMCs) lesions play an important role in atherosclerosis. The latest findings indicate that green tea extract has potential benefits for patients with atherosclerosis, but the components and mechanisms of action are unknown. (-)-Epicatechin gallate (ECG) is the main active ingredient extracted from green tea and has significant biological functions. However, the mechanism of ECG in atherosclerosis remains unclear. Therefore, we investigated the intervention of ECG on VSMCs induced by oxidized low-density lipoprotein (ox-LDL). The results show that ECG reduces the inflammatory response by preventing the overproduction of inflammatory mediators in VSMCs. ECG regulates the cell cycle and down-regulates the expression of proliferating cell nuclear antigen (PCNA) and cyclinD1, and then exerts an anti-proliferative effect. Furthermore, inhibition of the expression of matrix metalloproteinase 2 (MMP-2) and intercellular adhesion molecule 1 (ICAM-1) may be the mechanism by which ECG inhibits the migration of ox-LDL-induced VSMCs. Oil red O staining results show that ECG can improve cell foaming and reduce the content of total cholesterol (TC). In addition, ECG significantly reduces reactive oxygen species activity and also reduces the expression of p-p38, p-JNK, p-ERK1/2, p-IκBα, p-NF-κBp65, and TLR4. These results indicate that ECG has potential clinical applications for preventing atherosclerosis.

Infestation of Field Dodder (Cuscuta campestris Yunck.) Promotes Changes in Host Dry Weight and Essential Oil Production in Two Aromatic Plants, Peppermint and Chamomile

Peppermint (Mentha piperita L.) and chamomile (Chamomilla recutita (L.) Rausch.) are aromatic plants with considerable economic value. These plants and their essential oils are used in medicine, cosmetics, and the food industry. One of the main limiting factors in peppermint and chamomile commercial cultivation is weed competition since weeds are able to decrease both oil amount and biomass yield. The purpose of the present study was to determine the effect of parasitism by field dodder (Cuscuta campestris Yunck.) on peppermint and chamomile dry weight and their essential oil yield and composition. Essential oils from both noninfested and infested peppermint and chamomile plants were obtained by hydrodistillation and characterized chemically by gas chromatography (GC) coupled with mass spectrometry (MS). The amount of dry matter accumulated by peppermint and chamomile plants infested by field dodder was lower (25% and 63%, respectively) compared to noninfested plants. Essential oil yield increased for peppermint (3.87% (v/w) and 3.63% (v/w)), but decreased for chamomile (0.2% (v/w) and 0.5% (v/w)) both from infested and noninfested plants, respectively. The oil composition profile significantly differed in terms of content. In peppermint plants, field dodder infestation increased menthone content by 23%, and decreased the content of both menthol by 11% and pulegone by 67%. Furthermore, δ-cadinene was detected only in oil extracted from infested peppermint plants. Compared to peppermint, chamomile plants were significantly more affected by field dodder in terms of essential oil yield, as well as oil composition and plant dry weight. In chamomile plants, (E)-dendrolasin was detected in the oil of noninfested plants, and 1,4-dimethyl-7-(1-methylethyl)-azulen-2-ol was detected only in the oil of infested plants.