scholarly journals NopL, an Effector Protein of Rhizobium sp. NGR234, Thwarts Activation of Plant Defense Reactions

2004 ◽  
Vol 134 (2) ◽  
pp. 871-879 ◽  
Author(s):  
Alexander V. Bartsev ◽  
William J. Deakin ◽  
Nawal M. Boukli ◽  
Crystal B. McAlvin ◽  
Gary Stacey ◽  
...  
Keyword(s):  
Plant Defense ◽  
Effector Protein ◽  
Defense Reactions ◽  
Rhizobium Sp

scholarly journals Treatment with the Mycoparasite Pythium oligandrum Triggers Induction of Defense-Related Reactions in Tomato Roots When Challenged with Fusarium oxysporum f. sp. radicis-lycopersici

1997 ◽  
Vol 87 (1) ◽  
pp. 108-122 ◽  
Author(s):  
Nicole Benhamou ◽  
Patrice Rey ◽  
Mohamed Chérif ◽  
John Hockenhull ◽  
Yves Tirilly
Keyword(s):  
Plant Defense ◽  
Fusarium Oxysporum ◽  
Host Cell ◽  
Cell Walls ◽  
Pythium Oligandrum ◽  
Tomato Plants ◽  
Host Cytoplasm ◽  
Defense Reactions ◽  
Tomato Roots ◽  
Root Tissues

The influence exerted by the mycoparasite Pythium oligandrum in triggering plant defense reactions was investigated using an experimental system in which tomato plants were infected with the crown and root rot pathogen Fusarium oxysporum f. sp. radicis-lycopersici. To assess the antagonistic potential of P. oligandrum against F. oxysporum f. sp. radicis-lycopersici, the interaction between the two fungi was studied by scanning and transmission electron microscopy (SEM and TEM, respectively). SEM investigations of the interaction region between the fungi demonstrated that collapse and loss of turgor of F. oxysporum f. sp. radicis-lycopersici hyphae began soon after close contact was established with P. oligandrum. Ultrastructural observations confirmed that intimate contact between hyphae of P. oligandrum and cells of the pathogen resulted in a series of disturbances, including generalized disorganization of the host cytoplasm, retraction of the plasmalemma, and, finally, complete loss of the protoplasm. Cytochemical labeling of chitin with wheat germ agglutinin (WGA)/ovomucoid-gold complex showed that, except in the area of hyphal penetration, the chitin component of the host cell walls was structurally preserved at a time when the host cytoplasm had undergone complete disorganization. Interestingly, the same antagonistic process was observed in planta. The specific labeling patterns obtained with the exoglucanase-gold and WGA-ovomucoid-gold complexes confirmed that P. oligandrum successfully penetrated invading cells of the pathogen without causing substantial cell wall alterations, shown by the intense labeling of chitin. Cytological investigations of samples from P. oligandrum-inoculated tomato roots revealed that the fungus was able to colonize root tissues without inducing extensive cell damage. However, there was a novel finding concerning the structural alteration of the invading hyphae, evidenced by the frequent occurrence of empty fungal shells in root tissues. Pythium ingress in root tissues was associated with host metabolic changes, culminating in the elaboration of structural barriers at sites of potential fungal penetration. Striking differences in the extent of F. oxysporum f. sp. radicis-lycopersici colonization were observed between P. oligandrum-inoculated and control tomato plants. In control roots, the pathogen multiplied abundantly through much of the tissues, whereas in P. oligandrum-colonized roots pathogen growth was restricted to the outermost root tissues. This restricted pattern of pathogen colonization was accompanied by deposition of newly formed barriers beyond the infection sites. These host reactions appeared to be amplified compared to those seen in nonchallenged P. oligandrum-infected plants. Most hyphae of the pathogen that penetrated the epidermis exhibited considerable changes. Wall appositions contained large amounts of callose, in addition to be infiltrated with phenolic compounds. The labeling pattern obtained with gold-complexed laccase showed that phenolics were widely distributed in Fusarium-challenged P. oligandrum-inoculated tomato roots. Such compounds accumulated in the host cell walls and intercellular spaces. The wall-bound chitin component in Fusarium hyphae colonizing P. oligandrum-inoculated roots was preserved at a time when hyphae had undergone substantial degradation. These observations provide the first convincing evidence that P. oligandrum has the potential to induce plant defense reactions in addition to acting as a mycoparasite.

scholarly journals Proteasome comprising a β1 inducible subunit acts as a negative regulator of NADPH oxidase during elicitation of plant defense reactions

FEBS Letters ◽  
2005 ◽  
Vol 579 (21) ◽  
pp. 4879-4886 ◽  
Author(s):  
José Lequeu ◽  
Françoise Simon-Plas ◽  
Jérome Fromentin ◽  
Philippe Etienne ◽  
Anne-Sophie Petitot ◽  
...  
Keyword(s):  
Nadph Oxidase ◽  
Plant Defense ◽  
Negative Regulator ◽  
Defense Reactions

Wound age and infection of peach bark by Cytospora leucostoma

1986 ◽  
Vol 64 (10) ◽  
pp. 2319-2321 ◽  
Author(s):  
A. R. Biggs
Keyword(s):  
Plant Defense ◽  
Critical Period ◽  
Fungal Colonization ◽  
Wound Age ◽  
Defense Reactions ◽  
Close Proximity ◽  
Colonization Frequency ◽  
Histochemical Changes ◽  
Periderm Formation

Peach bark wounds of varying ages were inoculated with mycelium of Cytospora leucostoma (Pers.) Fr., and colonization frequency and extent were determined. Noninoculated wounds of similar ages and in close proximity to inoculated wounds were also sampled and examined histologically for morphological and histochemical changes associated with nonspecific plant defense reactions, including lignification and formation of lignosuberized tissue and new periderm. Results demonstrated that lignified and lignosuberized tissues significantly decreased the rate of fungal colonization, whereas new periderm with at least three cells thickness of new phellem completely inhibited fungal colonization. The critical period regarding effective periderm formation was between 10 and 14 days postwounding.

scholarly journals Priming Effect of Thiamine on the Enhancement of Induced Resistance to the Plant Disease Phytophthora Nicotianae in Tobacco

2021 ◽  
Author(s):  
Liu Tao ◽  
Tian Suohui ◽  
Chen Yanping ◽  
Zi Shuhui ◽  
Mei Jian ◽  
...  
Keyword(s):  
Plant Defense ◽  
Induced Resistance ◽  
Priming Effect ◽  
Plant Disease ◽  
Plant Defence ◽  
Vitamin B1 ◽  
Phytophthora Nicotianae ◽  
Callose Deposition ◽  
Pronounced Increase ◽  
Defense Reactions

Abstract Induced resistance by elicitors is considered to be an eco-friendly strategy to stimulate plant defense against pathogen attack. Thiamine (vitamin B1,VB1) can act as a plant defence trigger, or priming agent, leading to a rapid counterattack on pathogen invasion.To date, the mechanisms by which VB1 provides protection against plant disease have yet to be fully elucidated, expecially no reports about VB1 treatment influenced the development of Phytophthora nicotianae in plant. Tobacco black shank (TBS) caused by P. nicotianae is destructive to almost all tobacco cultivars and is widespread in many tobacco-growing countries. In the present study, the priming effect of VB1 on tobacco against the disease P. nicotianae and its biochemical and molecular impact on plant defense mechanisms were evaluated. Base on the effect of VB1 on mycelial growth and zoospore formation, the appropriate VB1 treatment was used in protecting tobacco against P. nicotianae. For VB1 pretreatment, tobacco exhibited a significant reduction in disease severity. Consistent with the occurrence of induced resistance, the pronounced increase in H2O2 level, phenylalanine ammonia lyase (PAL) and peroxidase (POD) activities were observed. For defense reactions, VB1 promoted the increases of H2O2, SA and lignin contents. Moreover, the expressions of PR1, PR5, NPR1, PAL, CM1, H1N1 and EFE26 were induced by VB1, which also involved in defense reactions. Our findings indicate that the priming effect of VB1 may partially depend on the production of the callose deposition, H2O2 accumulation, and hormone SA production.

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