scholarly journals Root-Associated Entomopathogenic Fungi Modulate Their Host Plant’s Photosystem II Photochemistry and Response to Herbivorous Insects

Molecules ◽  
2021 ◽  
Vol 27 (1) ◽  
pp. 207
Author(s):  
Julietta Moustaka ◽  
Nicolai Vitt Meyling ◽  
Thure Pavlo Hauser
Keyword(s):  
Photosystem Ii ◽  
Entomopathogenic Fungi ◽  
Spodoptera Exigua ◽  
Beet Armyworm ◽  
Larval Feeding ◽  
Tomato Plants ◽  
Photosystem Ii Photochemistry ◽  
Before And After ◽  
Negative Effect ◽  
Energy Dissipated

The escalating food demand and loss to herbivores has led to increasing interest in using resistance-inducing microbes for pest control. Here, we evaluated whether root-inoculation with fungi that are otherwise known as entomopathogens improves tomato (Solanum lycopersicum) leaflets’ reaction to herbivory by Spodoptera exigua (beet armyworm) larvae using chlorophyll fluorescence imaging. Plants were inoculated with Metarhizium brunneum or Beauveria bassiana, and photosystem II reactions were evaluated before and after larval feeding. Before herbivory, the fraction of absorbed light energy used for photochemistry (ΦPSII) was lower in M. brunneum-inoculated than in control plants, but not in B. bassiana-inoculated plants. After herbivory, however, ΦPSII increased in the fungal-inoculated plants compared with that before herbivory, similar to the reaction of control plants. At the same time, the fraction of energy dissipated as heat (ΦNPQ) decreased in the inoculated plants, resulting in an increased fraction of nonregulated energy loss (ΦNO) in M. brunneum. This indicates an increased singlet oxygen (1O2) formation not detected in B. bassiana-inoculated plants, showing that the two entomopathogenic fungi differentially modulate the leaflets’ response to herbivory. Overall, our results show that M. brunneum inoculation had a negative effect on the photosynthetic efficiency before herbivory, while B. bassiana inoculation had no significant effect. However, S. exigua leaf biting activated the same compensatory PSII response mechanism in tomato plants of both fungal-inoculated treatments as in control plants.

scholarly journals Identification of Bacillus thuringiensisDelta-Endotoxin Cry1C Domain III Amino Acid Residues Involved in Insect Specificity

1999 ◽  
Vol 65 (10) ◽  
pp. 4369-4374 ◽  
Author(s):  
Ruud A. de Maagd ◽  
Petra Bakker ◽  
Nikola Staykov ◽  
Stefan Dukiandjiev ◽  
Willem Stiekema ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Spodoptera Exigua ◽  
Specific Activity ◽  
Beet Armyworm ◽  
Amino Acid Residues ◽  
Optimal Activity ◽  
Amino Acid Insertion ◽  
Negative Effect ◽  
Domain Iii

ABSTRACT Cry1C domain III amino acid residues involved in specificity for beet armyworm (Spodoptera exigua) were identified. For this purpose, intradomain III hybrids between Cry1E (nontoxic) and Cry1E-Cry1C hybrid G27 (toxic) were made. Crossover points of these hybrids defined six sequence blocks containing between 1 and 19 of the amino acid differences between Cry1E and G27. Blocks B, C, D, and E of G27 were shown to be required for optimal activity against S. exigua. Block E was also required for optimal activity against the tobacco hornworm (Manduca sexta), whereas block D had a negative effect on toxicity for this insect. The mutagenesis of individual amino acids in block B identified Trp-476 as the only amino acid in this block essential, although not sufficient by itself, for full S. exigua activity. In block D, we identified a seven-amino-acid insertion in G27 that was not in Cry1E. The deletion of either one of two groups of four consecutive amino acids in this insertion completely abolished activity against S. exiguabut resulted in higher activity against M. sexta. Alanine substitutions of the first group had little effect on toxicity, whereas alanine substitutions of the second group had the same effect as its deletion. These results identify groups of amino acids as well as some individual residues in Cry1C domain III, which are strongly involved inS. exigua-specific activity as well as sometimes involved in M. sexta-specific activity.

Fluorescent Brighteners Can Enhance or Inhibit the Nucleopolyhedrovirus of the Diamondback Moth (Lepidoptera: Plutellidae)2

2004 ◽  
Vol 39 (1) ◽  
pp. 30-45 ◽  
Author(s):  
Robert R. Farrar ◽  
Martin Shapiro ◽  
A. H. McIntosh
Keyword(s):  
Plutella Xylostella ◽  
Helicoverpa Zea ◽  
Spodoptera Exigua ◽  
Diamondback Moth ◽  
Corn Earworm ◽  
Beet Armyworm ◽  
Disulfonic Acid ◽  
Host Insect ◽  
Negative Effect ◽  
Anagrapha Falcifera

The nucleopolyhedrovirus of the diamondback moth, Plutella xylostella (L.), (PxMNPV) was the most potent of three viruses tested against this insect. The potency of PxMNPV could be increased by the addition of certain diaminostilbene disulfonic acid-derived fluorescent brighteners, including Blankophor P167® at a concentration of 1%. Other fluorescent brighteners, including Blankophor HRS® at 1%, reduced the activity of PxMNPV, though lower concentrations of Blankophor HRS (0.25 to 0.5%) enhanced activity. In contrast, Blankophor HRS at 1% enhanced the nucleopolyhedrovirus of the celery looper, Anagrapha falcifera (Kirby), (AfMNPV) against the diamondback moth. Similar results were found in the corn earworm, Helicoverpa zea (Boddie), and the beet armyworm, Spodoptera exigua (Hübner), which are also susceptible to both PxMNPV and AfMNPV. Consumption of foliage treated with Blankophor HRS (0.5 to 1.0%) did not differ from that of foliage treated with similar concentrations of Blankophor P167. These results indicate a negative effect of higher concentrations of Blankophor HRS on PxMNPV, rather than on the host insect.

scholarly journals Rhizosphere-enriched microbes as a pool to design synthetic communities for reproducible beneficial outputs

2019 ◽  
Author(s):  
Maria-Dimitra Tsolakidou ◽  
Ioannis A Stringlis ◽  
Natalia Fanega-Sleziak ◽  
Stella Papageorgiou ◽  
Antria Tsalakou ◽  
...  
Keyword(s):  
Antifungal Activity ◽  
Fungal Pathogens ◽  
Growth Parameters ◽  
Tomato Plants ◽  
Beneficial Effects ◽  
Negative Effect ◽  
Tomato Growth ◽  
In Vitro Antifungal Activity

Abstract Composts represent a sustainable way to suppress diseases and improve plant growth. Identification of compost-derived microbial communities enriched in the rhizosphere of plants and characterization of their traits, could facilitate the design of microbial synthetic communities (SynComs) that upon soil inoculation could yield consistent beneficial effects towards plants. Here, we characterized a collection of compost-derived bacteria, previously isolated from tomato rhizosphere, for in vitro antifungal activity against soil-borne fungal pathogens and for their potential to change growth parameters in Arabidopsis. We further assessed root-competitive traits in the dominant rhizospheric genus Bacillus. Certain isolated rhizobacteria displayed antifungal activity against the tested pathogens and affected growth of Arabidopsis, and Bacilli members possessed several enzymatic activities. Subsequently, we designed two SynComs with different composition and tested their effect on Arabidopsis and tomato growth and health. SynCom1, consisting of different bacterial genera, displayed negative effect on Arabidopsis in vitro, but promoted tomato growth in pots. SynCom2, consisting of Bacilli, didn't affect Arabidopsis growth, enhanced tomato growth and suppressed Fusarium wilt symptoms. Overall, we found selection of compost-derived microbes with beneficial properties in the rhizosphere of tomato plants, and observed that application of SynComs on poor substrates can yield reproducible plant phenotypes.

scholarly journals Caterpillar salivary enzymes: "eliciting" a response

2004 ◽  
Vol 85 (1) ◽  
pp. 33-37 ◽  
Author(s):  
Magali Merkx-Jacques ◽  
Jacqueline C. Bede
Keyword(s):  
Artificial Diet ◽  
Spodoptera Exigua ◽  
Induced Defense ◽  
Defense Responses ◽  
Beet Armyworm ◽  
Herbivorous Insect ◽  
Plant Responses ◽  
Plant Defense Responses ◽  
Induced Defense Responses ◽  
Bertha Armyworm

Abstract Plants exhibit remarkable plasticity in their ability to differentiate between herbivorous insect species and subtly adjust their defense responses to target distinct pests. One key mechanism used by plants to recognize herbivorous caterpillars is elicitors present in their oral secretions; however, these elicitors not only cause the induction of plant defenses but recent evidence suggests that they may also suppress plant responses. The absence of “expected changes” in induced defense responses of insect-infested plants has been attributed to hydrogen peroxide produced by caterpillar salivary glucose oxidase (GOX). Activity of this enzyme is variable among caterpillar species; it was detected in two generalist caterpillars, the beet armyworm (Spodoptera exigua) and the bertha armyworm (Mamestra configurata), but not in other generalist or specialist caterpillar species tested. In the beet armyworm, GOX activity fluctuated over larval development with high activity associated with the salivary glands of fourth instars. Larval salivary GOX activity of the beet armyworm and the bertha armyworm was observed to be significantly higher in caterpillars reared on artificial diet as compared with those reared on Medicago truncatula plants. This implies that a factor in the diet is involved in the regulation of caterpillar salivary enzyme activity. Therefore, plant diet may be regulating caterpillar oral elicitors that are involved in the regulation of plant defense responses: our goal is to understand these two processes.

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