• The Plant Pathology Journal
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• v.24 no.4
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• pp.367-374
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• 2008

The genomes of plants contain more than 600 genes encoding a diverse set of proteases and the subunits of proteasomes. These proteases and proteasomes consist of plant proteolytic systems, which are involved in various cellular metabolic processes. Plant proteolytic systems have been shown to have diverse roles in defense responses, such as execution of the attack on the invading organisms, participation in signaling cascades, and perception of the invaders. In order to provide a framework for illustrating the importance of proteolytic systems in plant defense, characteristics of non-proteasome proteases and the 26S proteasome are summarized. The involvement of caspase-like proteases, saspases, apoplastic proteases, and the 26S proteasome in pathogen defense suggests that plant proteolytic systems are essential for defense and further clarity on the roles of plant proteases in defense is challenging but fundamentally important to understand plant-microbe interactions.

• Journal of Ecology and Environment
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• v.45 no.3
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• pp.143-151
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• 2021

Background: Plants are able to optimize defense responses induced by various herbivores, which have different feeding strategies. Local and systemic responses within a plant after herbivory are essential to modulate herbivore-specific plant responses. For instance, leaf-chewing herbivores elicit jasmonic acid signaling, which result in the inductions of toxic chemicals in the attacked leaf (tissue-specific responses) and also in the other unattacked parts of the plant (systemic responses). Root herbivory induces toxic metabolites in the attacked root and alters the levels of transcripts and metabolites in the unattacked shoot. However, we have little knowledge of the local and systemic responses against stem-boring herbivores. In this study, we examined the systemic changes in metabolites in the wild tobacco Nicotiana attenuata, when the stem-boring herbivore Trichobaris mucorea attacks. Results: To investigate the systemic responses of T. mucorea attacks, we measured the levels of jasmonic acid (JA), JA-dependent secondary metabolites, soluble sugars, and free amino acids in 7 distinct tissues of N. attenuata: leaf lamina with epidermis (LLE), leaf midrib (LM), stem epidermis (SE), stem pith (SP), stem vascular bundle (SV), root cortex with epidermis (RCE), and root vascular bundle (RV). The levels of JA were increased in all root tissues and in LM by T. mucorea attacks. The levels of chlorogenic acids (CGAs) and nicotine were increased in all stem tissues by T. mucorea. However, CGA was systematically induced in LM, and nicotine was systematically induced in LM and RCE. We further tested the resource allocation by measuring soluble sugars and free amino acids in plant tissues. T. mucorea attacks increased the level of free amino acids in all tissues except in LLE. The levels of soluble sugars were significantly decreased in SE and SP, but increased in RV. Conclusions: The results reveal that plants have local- and systemic-specific responses in response to attack from a stem-boring herbivore. Interestingly, the level of induced secondary metabolites was not consistent with the systemic inductions of JA. Spatiotemporal resolution of plant defense responses against stem herbivory will be required to understand how a plant copes with attack from herbivores from different feeding guilds.

• Korean Journal Plant Pathology
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• v.14 no.3
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• pp.278-285
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• 1998

Effects of chitosan on growth of tomato plant, and suppression of Fusaruim wilt caused by Fusarium oxysporum f. sp. lycopersici and late blight casued by Phytophthora infestans, were examined. Both late blight and fusarium wilt were suppressed by spray and irrigation of chitosan, respectively. Inhibition of mycelial growth was not greatly affected by molecular size of chitosan but, concentration dependent effects was observed. Ninty percent of P. infestans and 80% of F. oxysporum f. sp. lycopersici of mycelial growth was inhibited by 1,000 ppm of chitosan (MW 30,000~50,000) when amended in plate media. Induction of defense-related gene expression in plant by chitosan treatments were observed when chitosan treated tobacco and tomato RNA samples were hybridized with several defense-related genes as probes. The results revealed that $\beta$-1,3-glucanase and chitinase genes were strongly induced, while pathogenesis-related protein-1, 3-hydroxy-3-methylglutaryl coenzyme A reductase, anionic peroxidase, phenylalanine ammonia lyase genes were weakly induced by chitosan treatment. These results suggest that chitosan have dual effects on these host-pathogen interactions. Possible roles of chitosan in suppression of tomato diseases by inhibition of mycelial growth and activation of plant defense responses are discussed.

• Journal of Ginseng Research
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• v.35 no.1
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• pp.1-11
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• 2011

Korean ginseng is a medicinally important perennial herb from the family Araliaceae. It has been cultivated for its highly valued medicinal properties for over 1,000 years in east Asian countries such as China, Korea, and Japan. Due to its longtime cultivation in shady areas, ginseng is frequently exposed to pathogenic infections. Plants protect themselves from microbial pathogens using an array of defense mechanisms, some of which are constitutively active, while others are activated upon pathogen invasion. These induced defense responses, controlled by defense-related genes, require tradeoffs in terms of plant fitness. We hypothesize that ginseng, as with other plants, possesses regulatory mechanisms that coordinate the activation of attacker-specific defenses in order to minimize fitness costs while attaining optimal resistance. Several classes of defense-related genes are induced by infection, wounds, irradiation, and other abiotic stresses. Both salicylates and jasmonates have been shown to cause such responses, although their specific roles and interactions in signaling and development are not fully understood in ginseng. This review summarizes possible defense-related genes in ginseng based on their expression patterns against biotic and abiotic stresses and describes their functional roles.

• Animal cells and systems
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• v.3 no.3
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• pp.247-252
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• 1999

The aim of this study was to characterize antipredator tactics of anurans and to evaluate the effectiveness of these tactics for predator avoidance in real confrontations. Two types of experiments were conducted. In one experiment, one predator and one prey were placed together for one hour in a small confined space (one-to-one interaction). In another experiment, one predator and several prey were placed together for one day in a large enclosure in a field (field-based interaction). The prey consisted of three anuran species, Rana nigromaculata, R. rugosa, and Bombina orientalls: a snake species, Rhabdophis tigrinus tigrinus, was used as a predator. Results of both experiments demonstrated a range in antipredator responses of the frogs, from toxicity and warning coloration, coupled with slow responses in Bombina to little (or only slight) toxicity, crypsis, and fast take-off responses to the predator in the ranids. oth ranid species exhibited lower survival(57%) than Bombina (95%) in the field-based interaction, suggesting that motor responses of the palatable prey due to attacks of the predator ultimately limited their survival. The jumping of the ranids increased the activity of the predator, which became more likely to strike. Simple crouching(seen in R. rugosa and B. orientalis) and chemical defense (in Bombina) reduced predatory attacks.

• Structural Engineering and Mechanics
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• v.84 no.5
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• pp.675-684
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• 2022

The conventional single-degree-of-freedom (SDOF) system is appropriate for dynamic response analysis of paneltype structures without an opening. However, the typical building structures usually have four-sided fixed walls having an opening. Therefore, it may induce a considerable error when dynamic responses are estimated based on the conventional SDOF system, since the SDOF system cannot consider the effect of an opening during the SDOF analysis. For this reason, this study proposes a new SDOF system to consider the effect of an opening by adjusting its load-mass factor. The load-mass factor can be modified based on the assumption that the behaviors of the four-sided fixed wall with an opening is very similar to the behaviors of the same size wall without an opening, when the uniformly distributed blast loaded area is identical. In order to confirm a feasibility of the proposed SDOF system, a series of numerical simulations were carried out for the four-sided fixed reinforced concrete (RC) wall under a blast load. The dynamic responses estimated from the proposed SDOF system and the conventional SDOF system were compared with the dynamic responses evaluated from the finite element (FE) analysis. Especially, for the maximum dynamic responses except for 50% opening case, the proposed SDOF system had about 1.1% to 25.7% normalized errors while the conventional SDOF system had about 4.1% to 49.1% normalized errors.

• The Plant Pathology Journal
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• v.39 no.5
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• pp.449-465
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• 2023

Plants are challenged by various pathogens throughout their lives, such as bacteria, viruses, fungi, and insects; consequently, they have evolved several defense mechanisms. In addition, plants have developed localized and systematic immune responses due to biotic and abiotic stress exposure. Animals are known to activate DNA damage responses (DDRs) and DNA damage sensor immune signals in response to stress, and the process is well studied in animal systems. However, the links between stress perception and immune response through DDRs remain largely unknown in plants. To determine whether DDRs induce plant resistance to pathogens, Arabidopsis plants were treated with bleomycin, a DNA damage-inducing agent, and the replication levels of viral pathogens and growth of bacterial pathogens were determined. We observed that DDR-mediated resistance was specifically activated against viral pathogens, including turnip crinkle virus (TCV). DDR increased the expression level of pathogenesis-related (PR) genes and the total salicylic acid (SA) content and promoted mitogen-activated protein kinase signaling cascades, including the WRKY signaling pathway in Arabidopsis. Transcriptome analysis further revealed that defense-and SA-related genes were upregulated by DDR. The atm-2atr-2 double mutants were susceptible to TCV, indicating that the main DDR signaling pathway sensors play an important role in plant immune responses. In conclusion, DDRs activated basal immune responses to viral pathogens.

• Proceedings of the Botanical Society of Korea Conference
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• 1998.07a
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• pp.10-18
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• 1998

For improvement of plants in disease resistance, it is most important to elucidate the mechanism to perceive and respond to the signal molecules of invaders. A model system with pea and its pathogen, Mycosphaerella pinodes, showed that the fungal elicitor induced defense responses in all plant species tested but that the suppressor of the fungus blocked or delayed the expression of defense responses and induced accessibility only in the host plant. In the world, many researchers believe that the pathogens` signals are recognized only on the receptors in the plasma membranes. Though we found that the ATPase and polyphosphoinositide metabolism in isolated plasma membranes responded to these fungal signals, we failed to detect specific actions of the suppressor in vitro on these plasma membrane functions. Recently, we found that ATPase (NTPases) and superoxide generating system in isolated cell wall were regulated by these fungal signals even in vitro, especially, by the suppressor in a strictly species-specific manner and also that the cell wall alone prepared an original defense system. The effects of both fungal signals on the isolated cell wall functions in vitro coincide perfectly with those on defense responses in vivo. In this treatise, we discuss the key role of the cell wall, which is plant-specific and the most exterior organelle, in determining host-parasite specificity and molecular target for improvement of plants.

• Plant Biotechnology Reports
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• v.5 no.4
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• pp.353-365
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• 2011

The present study investigates the possible regulatory role of exogenous nitric oxide (NO) in antioxidant defense and methylglyoxal (MG) detoxification systems of wheat seedlings exposed to salt stress (150 and 300 mM NaCl, 4 days). Seedlings were pre-treated for 24 h with 1 mM sodium nitroprusside, a NO donor, and then subjected to salt stress. The ascorbate (AsA) content decreased significantly with increased salt stress. The amount of reduced glutathione (GSH) and glutathione disulfide (GSSG) and the GSH/GSSG ratio increased with an increase in the level of salt stress. The glutathione S-transferase (GST) activity increased significantly with severe salt stress (300 mM). The ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), catalase (CAT) and glutathione peroxidase (GPX) activities did not show significant changes in response to salt stress. The glutathione reductase (GR), glyoxalase I (Gly I), and glyoxalase II (Gly II) activities decreased upon the imposition of salt stress, especially at 300 mM NaCl, with a concomitant increase in the $H_2O_2$ and lipid peroxidation levels. Exogenous NO pretreatment of the seedlings had little influence on the nonenzymatic and enzymatic components compared to the seedlings of the untreated control. Further investigation revealed that NO pre-treatment had a synergistic effect; that is, the pre-treatment increased the AsA and GSH content and the GSH/GSSG ratio, as well as the activities of MDHAR, DHAR, GR, GST, GPX, Gly I, and Gly II in most of the seedlings subjected to salt stress. These results suggest that the exogenous application of NO rendered the plants more tolerant to salinity-induced oxidative damage by enhancing their antioxidant defense and MG detoxification systems.

• BMB Reports
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• v.55 no.7
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• pp.342-347
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• 2022

Defense priming allows plants to enhance their immune responses to subsequent pathogen challenges. Recent reports suggested that acquired resistances in parental generation can be inherited into descendants. Although epigenetic mechanisms are plausible tools enabling the transmission of information or phenotypic traits induced by environmental cues across generations, the mechanism for the transgenerational inheritance of defense priming in plants has yet to be elucidated. With the initial aim to elucidate an epigenetic mechanism for the defense priming in plants, we reassessed the transgenerational inheritance of plant defense, however, could not observe any evidence supporting it. By using the same dipping method with previous reports, Arabidopsis was exposed repeatedly to Pseudomonas syringae pv tomato DC3000 (Pst DC3000) during vegetative or reproductive stages. Irrespective of the developmental stages of parental plants that received pathogen infection, the descendants did not exhibit primed resistance phenotypes, defense marker gene (PR1) expression, or elevated histone acetylation within PR1 chromatin. In assays using the pressure-infiltration method for infection, we obtained the same results as above. Thus, our results suggest that the previous observations on the transgenerational inheritance of defense priming in plants should be more extensively and carefully reassessed.