New Insights into Plants’ Defense Mechanisms against Biotic Stresses

A special issue of Plants (ISSN 2223-7747). This special issue belongs to the section "Plant Protection and Biotic Interactions".

Deadline for manuscript submissions: closed (30 June 2022) | Viewed by 18717

Special Issue Editor

Institut de Biologie Moléculaire des Plantes, University of Strasbourg, 67084 Strasbourg, France
Interests: plant physiology; genetics; plant molecular biology; biochemistry; phytohormones; metabolism; plant responses to biotic and abiotic stresses
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Special Issue Information

Dear Colleagues,

Over millions of years of co-evolution with pathogens and herbivores, plants have developed fascinating, diverse, and complex defense mechanisms. In addition to protective physical barriers and basal defenses, plants have acquired the ability to recognize pathogens and herbivores in order to induce precise and dynamic molecular mechanisms, including signaling cascades as well as hormonal and transcriptional regulations that induce defense responses, such as the synthesis of specialized metabolites and pathogenesis-related proteins. Although excellent research has already highlighted some core components of plant defenses, it remains a huge challenge to identify the genes as well as the cellular and molecular mechanisms involved in the defenses of plants against particular biotic stresses. Stress responses and defense mechanisms are especially complex because of crosstalk, spatio-temporal regulations, intricate metabolic networks, variations of specialized metabolites among plant species, and multiple defense responses against one threat. Better analytic tools to explore metabolomes and proteomes, genome sequencing, and improved genetic tools are now available to unravel the defense mechanisms against biotic stresses. Exploiting new knowledge of plants’ defense mechanisms will lead to the development of new varieties with enhanced protection against pathogens and pests, and will also ameliorate sustainable agriculture practices. This Special Issue of Plants welcomes articles (research articles, review articles, communications, methods, and short notes) that enhance our understanding of plants’ defense mechanisms against biotic stresses.

Dr. Emilie Widemann
Guest Editor

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Keywords

  • Plant defense
  • Stress responses
  • Specialized structures
  • Hormonal signaling
  • Molecular mechanisms
  • Gene expression regulations
  • Metabolism
  • Pathogens and pests
  • Plant–herbivore interactions

Published Papers (7 papers)

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Research

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11 pages, 1699 KiB  
Article
The Mutation of Rice MEDIATOR25, OsMED25, Induces Rice Bacterial Blight Resistance through Altering Jasmonate- and Auxin-Signaling
by Go Suzuki, Manatsu Fukuda, Nonawin Lucob-Agustin, Yoshiaki Inukai and Kenji Gomi
Plants 2022, 11(12), 1601; https://doi.org/10.3390/plants11121601 - 17 Jun 2022
Cited by 3 | Viewed by 2037
Abstract
Rice bacterial blight disease caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of the most severe diseases of rice. However, the regulatory mechanisms of rice defense against Xoo remain poorly understood. The rice MEDIATOR25, OsMED25—a subunit of the mediator multiprotein [...] Read more.
Rice bacterial blight disease caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of the most severe diseases of rice. However, the regulatory mechanisms of rice defense against Xoo remain poorly understood. The rice MEDIATOR25, OsMED25—a subunit of the mediator multiprotein complex that acts as a universal adaptor between transcription factors (TFs) and RNA polymerase II—plays an important role in jasmonic acid (JA)-mediated lateral root development in rice. In this study, we found that OsMED25 also plays an important role in JA- and auxin-mediated resistance responses against rice bacterial blight. The osmed25 loss-of-function mutant exhibited high resistance to Xoo. The expression of JA-responsive defense-related genes regulated by OsMYC2, which is a positive TF in JA signaling, was downregulated in osmed25 mutants. Conversely, expression of some OsMYC2-independent JA-responsive defense-related genes was upregulated in osmed25 mutants. Furthermore, OsMED25 interacted with some AUXIN RESPONSE FACTORS (OsARFs) that regulate auxin signaling, whereas the mutated osmed25 protein did not interact with the OsARFs. The expression of auxin-responsive genes was downregulated in osmed25 mutants, and auxin-induced susceptibility to Xoo was not observed in osmed25 mutants. These results indicate that OsMED25 plays an important role in the stable regulation of JA- and auxin-mediated signaling in rice defense response. Full article
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14 pages, 3044 KiB  
Article
A Putative Effector LtCSEP1 from Lasiodiplodia theobromae Inhibits BAX-Triggered Cell Death and Suppresses Immunity Responses in Nicotiana benthamiana
by Qikai Xing, Yang Cao, Junbo Peng, Wei Zhang, Jiahong Wu, Yueyan Zhou, Xinghong Li and Jiye Yan
Plants 2022, 11(11), 1462; https://doi.org/10.3390/plants11111462 - 30 May 2022
Cited by 1 | Viewed by 1688
Abstract
Lasiodiplodia theobromae is a causal agent of grapevine trunk disease, and it poses a significant threat to the grape industry worldwide. Fungal effectors play an essential role in the interaction between plants and pathogens. However, few studies have been conducted to understand the [...] Read more.
Lasiodiplodia theobromae is a causal agent of grapevine trunk disease, and it poses a significant threat to the grape industry worldwide. Fungal effectors play an essential role in the interaction between plants and pathogens. However, few studies have been conducted to understand the functions of individual effectors in L. theobromae. In this study, we identified and characterized a candidate secreted effector protein, LtCSEP1, in L. theobromae. Gene expression analysis suggested that transcription of LtCSEP1 in L. theobromae was induced at the early infection stages in the grapevine. Yeast secretion assay revealed that LtCSEP1 contains a functional signal peptide. Transient expression of LtCSEP1 in Nicotiana benthamiana suppresses BAX-trigged cell death and significantly inhibits the flg22-induced PTI-associated gene expression. Furthermore, the ectopic expression of LtCSEP1 in N. benthamiana enhanced disease susceptibility to L. theobromae by downregulating the defense-related genes. These results demonstrated that LtCSEP1 is a potential effector of L. theobromae, which contributes to suppressing the plant’s defenses. Full article
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12 pages, 1145 KiB  
Article
Negative Effects of Rhizobacteria Association on Plant Recruitment of Generalist Predators
by Tobias B. Löser, Dani Lucas-Barbosa, Monika Maurhofer, Mark C. Mescher and Consuelo M. De Moraes
Plants 2022, 11(7), 920; https://doi.org/10.3390/plants11070920 - 29 Mar 2022
Viewed by 1568
Abstract
Plant-associated microbes can influence above- and belowground interactions between plants and other organisms and thus have significant potential for use in the management of agricultural ecosystems. However, fully realizing this potential will require improved understanding of the specific ways in which microbes influence [...] Read more.
Plant-associated microbes can influence above- and belowground interactions between plants and other organisms and thus have significant potential for use in the management of agricultural ecosystems. However, fully realizing this potential will require improved understanding of the specific ways in which microbes influence plant ecology, which are both more complex and less well studied than the direct effects of microbes on host-plant physiology. Microbial effects on mutualistic and antagonistic interactions between plants and insects are of particular interest in this regard. This study examines the effects of two strains of Pseudomonas rhizobacteria on the direct and indirect (predator-mediated) resistance of tomato plants to a generalist herbivore (Spodoptera littoralis) and associated changes in levels of defense compounds. We observed no significant effects of rhizobacteria inoculation on caterpillar weight, suggesting that rhizobacteria did not influence direct resistance. However, the generalist predator Podisus maculiventris avoided plants inoculated with one of our rhizobacteria strains, Pseudomonas simiae. Consistent with these results, we found that inoculation with P. simiae influenced plant volatile emissions, but not levels of defense-related compounds. These findings show that rhizobacteria can negatively affect the attraction of generalist predators, while highlighting the complexity and context dependence of microbial effects on plant–insect interactions. Full article
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14 pages, 3797 KiB  
Article
BnaA03.MKK5-BnaA06.MPK3/BnaC03.MPK3 Module Positively Contributes to Sclerotinia sclerotiorum Resistance in Brassica napus
by Ka Zhang, Chenjian Zhuo, Zhixin Wang, Fei Liu, Jing Wen, Bin Yi, Jinxiong Shen, Chaozhi Ma, Tingdong Fu and Jinxing Tu
Plants 2022, 11(5), 609; https://doi.org/10.3390/plants11050609 - 24 Feb 2022
Cited by 7 | Viewed by 2129
Abstract
Brassica napus (oilseed rape) is one of the most important oil crops worldwide, but its growth is seriously threatened by Sclerotinia sclerotiorum. The mechanism of oilseed rape response to this pathogen has rarely been studied. Here, it was identified that BnaA03.MKK5 whose [...] Read more.
Brassica napus (oilseed rape) is one of the most important oil crops worldwide, but its growth is seriously threatened by Sclerotinia sclerotiorum. The mechanism of oilseed rape response to this pathogen has rarely been studied. Here, it was identified that BnaA03.MKK5 whose expression was induced by S. sclerotiorum infection was involved in plant immunity. BnaA03.MKK5 overexpression lines exhibited decreased disease symptoms compared to wild-type plants, accompanied by the increased expression of camalexin-biosynthesis-related genes, including BnPAD3 and BnCYP71A13. In addition, two copies of BnMPK3 (BnA06.MPK3 and BnC03.MPK3) were induced by Sclerotinia incubation, and BnaA03.MKK5 interacted with BnaA06.MPK3/BnaC03.MPK3 in yeast. These interactions were confirmed using in vivo co-immunoprecipitation assays. In vitro phosphorylation assays showed that BnaA06.MPK3 and BnaC03.MPK3 were the direct phosphorylation substrates of BnaA03.MKK5. The transgenic oilseed rape plants including BnaA06.MPK3 and BnaC03.MPK3 overexpression lines and BnMPK3 gene editing lines mediated by CRISPR/Cas9 were generated; the results of the genetic transformation of BnaA06.MPK3/BnaC03.MPK3 indicate that BnMPK3 also has a positive role in Sclerotinia resistance. This study provides information about the potential mechanism of B. napus defense against S. Sclerotiorum mediated by a detailed BnaA03.MKK5-BnaA06.MPK3/BnaC03.MPK3 module. Full article
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18 pages, 3535 KiB  
Article
β-Cyclocitral, a Master Regulator of Multiple Stress-Responsive Genes in Solanum lycopersicum L. Plants
by Shreyas Deshpande, Vishwabandhu Purkar and Sirsha Mitra
Plants 2021, 10(11), 2465; https://doi.org/10.3390/plants10112465 - 15 Nov 2021
Cited by 7 | Viewed by 2374
Abstract
β-cyclocitral (βCC), a major apocarotenoid of β-carotene, enhances plants’ defense against environmental stresses. However, the knowledge of βCC’s involvement in the complex stress-signaling network is limited. Here we demonstrate how βCC reprograms the transcriptional responses that enable Solanum lycopersicum L. (tomato) plants to [...] Read more.
β-cyclocitral (βCC), a major apocarotenoid of β-carotene, enhances plants’ defense against environmental stresses. However, the knowledge of βCC’s involvement in the complex stress-signaling network is limited. Here we demonstrate how βCC reprograms the transcriptional responses that enable Solanum lycopersicum L. (tomato) plants to endure a plethora of environmental stresses. Comparative transcriptome analysis of control and βCC-treated tomato plants was done by generating RNA sequences in the BGISEQ-500 platform. The trimmed sequences were mapped on the tomato reference genome that identifies 211 protein-coding differentially expressed genes. Gene ontology and Kyoto Encyclopedia of Genes and Genomes analysis and their enrichment uncovered that only upregulated genes are attributed to the stress response. Moreover, 80% of the upregulated genes are functionally related to abiotic and biotic stresses. Co-functional analysis of stress-responsive genes revealed a network of 18 genes that code for heat shock proteins, transcription factors (TFs), and calcium-binding proteins. The upregulation of jasmonic acid (JA)-dependent TFs (MYC2, MYB44, ERFs) but not the JA biosynthetic genes is surprising. However, the upregulation of DREB3, an abscisic acid (ABA)-independent TF, validates the unaltered expression of ABA biosynthetic genes. We conclude that βCC treatment upregulates multiple stress-responsive genes without eliciting JA and ABA biosynthesis. Full article
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21 pages, 2278 KiB  
Article
Mixtures of Biological Control Agents and Organic Additives Improve Physiological Behavior in Cape Gooseberry Plants under Vascular Wilt Disease
by José Luis Chaves-Gómez, Cristian Camilo Chávez-Arias, Alba Marina Cotes Prado, Sandra Gómez-Caro and Hermann Restrepo-Díaz
Plants 2021, 10(10), 2059; https://doi.org/10.3390/plants10102059 - 29 Sep 2021
Cited by 5 | Viewed by 2075
Abstract
This study aimed to assess the soil application of mixtures of biological control agents (BCAs) (Trichoderma virens and Bacillus velezensis) and organic additives (chitosan and burnt rice husk) on the physiological and biochemical behavior of cape gooseberry plants exposed to Fusarium [...] Read more.
This study aimed to assess the soil application of mixtures of biological control agents (BCAs) (Trichoderma virens and Bacillus velezensis) and organic additives (chitosan and burnt rice husk) on the physiological and biochemical behavior of cape gooseberry plants exposed to Fusarium oxysporum f. sp. physali (Foph) inoculum. The treatments with inoculated and non-inoculated plants were: (i) T. virens + B. velezensis (Mix), (ii) T. virens + B. velezensis + burnt rice husk (MixRh), (iii) T. virens + B. velezensis + chitosan (MixChi), and (iv) controls (plants without any mixtures). Plants inoculated and treated with Mix or MixChi reduced the area under the disease progress curve (AUDPC) (57.1) and disease severity index (DSI) (2.97) compared to inoculated plants without any treatment (69.3 for AUDPC and 3.2 for DSI). Additionally, these groups of plants (Mix or MixChi) obtained greater leaf water potential (~−0.5 Mpa) and a lower MDA production (~12.5 µmol g−2 FW) than plants with Foph and without mixtures (−0.61 Mpa and 18.2 µmol g−2 FW, respectively). The results suggest that MixChi treatments may be a promising alternative for vascular wilt management in cape gooseberry crops affected by this disease. Full article
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Review

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13 pages, 2159 KiB  
Review
Plant Responses to Biotic Stress: Old Memories Matter
by Anirban Bhar, Amrita Chakraborty and Amit Roy
Plants 2022, 11(1), 84; https://doi.org/10.3390/plants11010084 - 28 Dec 2021
Cited by 26 | Viewed by 5318
Abstract
Plants are fascinating organisms present in most ecosystems and a model system for studying different facets of ecological interactions on Earth. In the environment, plants constantly encounter a multitude of abiotic and biotic stresses. The zero-avoidance phenomena make them more resilient to such [...] Read more.
Plants are fascinating organisms present in most ecosystems and a model system for studying different facets of ecological interactions on Earth. In the environment, plants constantly encounter a multitude of abiotic and biotic stresses. The zero-avoidance phenomena make them more resilient to such environmental odds. Plants combat biotic stress or pathogenic ingression through a complex orchestration of intracellular signalling cascades. The plant–microbe interaction primarily relies on acquired immune response due to the absence of any specialised immunogenic cells for adaptive immune response. The generation of immune memory is mainly carried out by T cells as part of the humoral immune response in animals. Recently, prodigious advancements in our understanding of epigenetic regulations in plants invoke the “plant memory” theory afresh. Current innovations in cutting-edge genomic tools have revealed stress-associated genomic alterations and strengthened the idea of transgenerational memory in plants. In plants, stress signalling events are transferred as genomic imprints in successive generations, even without any stress. Such immunogenic priming of plants against biotic stresses is crucial for their eco-evolutionary success. However, there is limited literature capturing the current knowledge of the transgenerational memory of plants boosting biotic stress responses. In this context, the present review focuses on the general concept of memory in plants, recent advancements in this field and comprehensive implications in biotic stress tolerance with future perspectives. Full article
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