Feng Zhu
Jing Shang2*
Sek-Man Wong- 1College of Plant Protection, Joint International Research Laboratory of Agriculture and Agri-Product Safety, the Ministry of Education of China, Yangzhou University, Yangzhou, Jiangsu, China
- 2College of Agronomy, Sichuan Agricultural University, Chengdu, Sichuan, China
- 3Department of Biological Sciences, National University of Singapore, Singapore, Singapore
- 4National University of Singapore Suzhou Research Institute, Suzhou Industrial Park, Suzhou, Jiangsu, China
Editorial on the Research Topic
Induced plant resistance against pathogens by application of bioactive molecules
Plants constantly face many kinds of pathogens, such as bacteria, oomycetes, fungi, viruses, and nematodes. Plant diseases caused by these pathogens may result in huge crop yields and quality losses (Savary et al., 2019; Zhu et al., 2023a). Currently, the application of conventional agrochemicals remains the main approach to control crop diseases in agricultural production. However, the ever-increasing environmental and social problems of agrochemicals such as pathogens resistance, destruction of ecological balance and biodiversity, and environmental pollution mean that ecologically safer and more sustainable technologies are urgently needed.
During the co-evolution between plants and pathogens, plants have evolved complex defense mechanisms and strategies against various pathogens infection. For example, PAMP-triggered immunity (PTI), effector-triggered immunity (ETI), systemic acquired resistance (SAR) and RNA interference (RNAi) are the major plant immune defense systems to protect the host from various pathogens attacks (Ngou et al., 2021; Yuan et al., 2021; Chang et al., 2022; Zhu et al., 2023b). Several studies indicated that the induction of plant immunity can be triggered by exogenous bioactive molecules, such as proteins, peptides, phytohormones, nanoparticles, oligosaccharides, microbial biocontrol agents, and so on. This has raised the prospect that induced plant resistance by application of bioactive molecules could serve as a sustainable approach in crop protection.
This Research Topic combines 6 publications, including 3 review articles and 3 research articles, covering several aspect of induced plant resistance. The featured in-depth topic reviews and research articles provide readers a convenient way to expand and understand the current knowledge and status of the induced plant resistance.
Exogenous application of inorganic salts significantly enhance resistance against various pathogens in multiple plant species (Deliopoulos et al., 2010; Zhu et al., 2023b). For example, application of K2HPO4 or KH2PO4 triggered the activities of defense-related enzymes in bean plants and increased resistance to Uromyces appendiculatus (Devi et al., 2020). Sun et al. have investigated the effects of exogenous application of sodium silicate (Na2SiO3·9H2O) on the occurrence of Fusarium wilt in cucumber and its mechanisms. They have provided evidence that exogenously applied silicon enhances resistance to cucumber wilt disease by up-regulating the antioxidant system, photosynthetic capacity, and stomatal opening in cucumber leaves.
The use of biological control agents for the management of plant pathogens is an ecologically safer and sustainable strategy in agriculture production (Köhl et al., 2019). Several biocontrol bacteria exhibit strong antimicrobial activities because they can produce various antimicrobial substances and induce host resistance against various plant pathogens. Yang et al. have isolated a potential biocontrol bacterium (Burkholderia gladioli strain KJ-34) from the rhizosphere soil of rice. They reveal that B. gladioli strain KJ-34 shows broad-spectrum strong antifungal activities against multiple fungal pathogens and produces various biological control metabolites such as benzoylstaurosporine, morellin and scopolamine. The KJ-34 not only inhibits mycelial growth and spore germination of multiple filamentous fungi but also induces resistance to Botrytis cinerea and Magnaporthe oryzae in tomato and rice, respectively.
Reactive oxygen species (ROS) and plant hormones, such as jasmonic acid (JA), salicylic acid (SA), and ethylene (ET) play important roles in plant immunity and resistance (Berens et al., 2017; Mittler et al., 2022). Su and Gassmann review how the host controls chloroplast ROS (cROS) accumulation during ETI. They summarize possible cytoplasmic regulatory mechanisms of cROS accumulation during ETI from three aspects, such as, selective mRNA decay, translational regulation, and autophagy-dependent formation of Rubisco-containing bodies (RCBs). Kesel et al. have provided an interesting finding that foliar diproline (cyclo(L-Pro-L-Pro)) treatment induces resistance to root-knot nematode Meloidogyne graminicola (Mg) in the same and subsequent rice generations. Furthermore, diproline-induced resistance against Mg in rice is associated with disturbances in the iron (Fe) homeostasis, ET and nitric oxide (NO) pathways.
Various kinds of oligosaccharides, such as chitosan, chitin, and β-glucans, function as PAMPs or DAMPs and consequently activate plant immunity (Guarnizo et al., 2020; Zhu et al., 2023b). Chitosan or its fragments have been shown to induce plant immunity against fungal pathogens in various crops. Mukarram et al. review the current knowledge of chitosan’s antimicrobial and insecticidal potential. Chitosan supports plant growth and development and protects against microbial entities such as fungi, bacteria, viruses, nematodes, and insects. They also summarize the action mechanism of chitosan-induced resistance against various pathogens and insects. The chitosan perception is proved to have crosstalk with several other signaling pathways, such as phytohormones (SA, indole acetic acid (IAA), gibberellic acid (GA), abscisic acid (ABA), JA), ROS and antioxidant metabolism, and cellular signaling molecules via Ca2+, NO, transcription factors (TFs), and defensive gene activation.
Pathogenesis-related proteins (PRs) are small proteins that play important roles in plant defense responses against biotic stresses (Kattupalli et al., 2021). Application of multiple bioactive molecules enhance host resistance against various pathogens through inducing the accumulation of PRs. Currently, PRs are divided into 17 families (PR-1 to PR-17) based on their physicochemical properties, such as defensins and chitinases. Lopes et al. comprehensively review the mechanisms of action of PR-10 in the plant’s defense response against biotic stresses (viruses, bacteria, fungi, oomycetes, nematodes and insects). They summarize the modes of action of PR-10 crosstalk with TFs, phytohormones pathways, physical interactions with effector proteins or pattern recognition receptors and other signaling molecules involved with the plant’s defense system.
We hope that this Research Topic helps readers to increase understanding of the molecular mechanisms and their potential applications in the activation of plant defense by bioactive molecules. A deeper understanding of the molecular mechanisms and their potential applications in the activation of plant defense by bioactive molecules will be crucial to developing effective and sustainable tools to control plant diseases in crop protection.
Author contributions
FZ: Funding acquisition, Writing – original draft, Writing – review & editing. JS: Writing – review & editing. SW: Writing – review & editing.
Funding
The work is supported by the Agricultural Science And Technology Independent Innovation Foundation of Jiangsu Province of China [CX (20)3128] and the Yangzhou University of ‘High-end Talent Support Program’ to FZ.
Conflict of interest
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
Publisher’s note
All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.
References
Berens, M. L., Berry, H. M., Mine, A., Argueso, C. T., Tsuda, K. (2017). Evolution of hormone signaling networks in plant defense. Annu. Rev. Phytopathol. 55, 401–425. doi: 10.1146/annurev-phyto-080516-035544
Chang, M., Chen, H., Liu, F., Fu, Z. Q. (2022). PTI and ETI: convergent pathways with diverse elicitors. Trends Plant Sci. 27, 113–115. doi: 10.1016/j.tplants.2021.11.013
Deliopoulos, T., Kettlewell, P. S., Hare, M. C. (2010). Fungal disease suppression by inorganic salts: a review. Crop Prot. 29, 1059–1075. doi: 10.1016/j.cropro.2010.05.011
Devi, B., Singh, G., Dash, A. K., Gupta, S. K. (2020). Chemically induced systemic acquired resistance in the inhibition of French bean rust. Curr. Plant Biol. 23, 100151. doi: 10.1016/j.cpb.2020.100151
Guarnizo, N., Oliveros, D., Murillo–Arango, W., Bermúdez–Cardona, M. B. (2020). Oligosaccharides: defense inducers, their recognition in plants, commercial uses and perspectives. Molecules 25, 5972. doi: 10.3390/molecules25245972
Kattupalli, D., Srinivasan, A., Soniya, E. V. (2021). A genome-wide analysis of pathogenesis-related protein-1 (PR-1) genes from piper nigrum reveals its critical role during phytophthora capsici infection. Genes 12, 1007. doi: 10.3390/genes12071007
Köhl, J., Kolnaar, R., Ravensberg, W. J. (2019). Mode of action of microbial biological control agents against plant diseases: relevance beyond efficacy. Front. Plant Sci. 10, 845. doi: 10.3389/fpls.2019.00845
Mittler, R., Zandalinas, S. I., Fichman, Y., Breusegem, F. V. (2022). Reactive oxygen species signalling in plant stress responses. Nat. Rev. Mol. Cell Biol. 23, 663–679. doi: 10.1038/s41580-022-00499-2
Ngou, B. P. M., Ahn, H. K., Ding, P. T., Jones, J. D. G. (2021). Mutual potentiation of plant immunity by cell–surface and intracellular receptors. Nature 592, 110–115. doi: 10.1038/s41586-021-03315-7
Savary, S., Willocquet, L., Pethybridge, S. J., Esker, P., McRoberts, N., Nelson, A. (2019). The global burden of pathogens and pests on major food crops. Nat. Ecol. Evol. 3, 430–439. doi: 10.1038/s41559-018-0793-y
Yuan, M., Jiang, Z., Bi, G., Nomura, K., Liu, M., Wang, Y., et al. (2021). Pattern–recognition receptors are required for NLR–mediated plant immunity. Nature 592, 105–109. doi: 10.1038/s41586-021-03316-6
Zhu, F., Cao, M. Y., Zhang, Q. P., Mohan, R., Schar, J., Mitchell, M., et al. (2023b). Join the green team: Inducers of plant immunity in the plant disease sustainable control toolbox. J. Adv. Res. doi: 10.1016/j.jare.2023.04.016
Keywords: induced plant immunity, PTI, ETI, SAR, RNAi, reactive oxygen species, plant hormones, bioactive molecules
Citation: Zhu F, Shang J and Wong S-M (2023) Editorial: Induced plant resistance against pathogens by application of bioactive molecules. Front. Plant Sci. 14:1282909. doi: 10.3389/fpls.2023.1282909
Received: 25 August 2023; Accepted: 14 September 2023;
Published: 20 September 2023.
Edited and Reviewed by:
Adam Schikora, Institute for Epidemiology and Pathogen Diagnostics, GermanyCopyright © 2023 Zhu, Shang and Wong. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: Feng Zhu, zhufeng@yzu.edu.cn; Jing Shang, shangjing@sicau.edu.cn; Sek-Man Wong, dbswsm@nus.edu.sg