AM Fungi in Plant Protection

Questions and Answers

What structural feature do mycorrhizal plants form around the sites of pathogen infection?

Vascular tissues

Cell walls

Papilla-like structures (correct)

Chloroplasts

Which compound's accumulation is significantly enhanced in mycorrhizal tomatoes upon Phytophthora attack?

Cellulose

Callose

PR-1a (correct)

Pectin

What type of pathogens did AM symbiosis induce systemic resistance against in tomato plants?

Bacterial pathogens

Fungal pathogens (correct)

Viral pathogens

Nematodes

Which signaling pathway is confirmed to be required for AM-induced resistance against Botrytis cinerea in tomatoes?

JA signaling Signup and view all the answers

In addition to the root system, where else has priming of defenses been shown in AM plants?

Leaves Signup and view all the answers

What is one direct mechanism by which AM fungi help reduce pathogenic fungi in plants?

Competition for carbon and nitrogen Signup and view all the answers

Which of the following changes in the plant is associated with root colonization by AM fungi?

Alteration in root architecture Signup and view all the answers

How do AM fungi influence plant defense mechanisms?

Through changes in genetic expression Signup and view all the answers

Which statement best describes the competitive interaction between AM fungi and pathogenic microorganisms?

AM fungi compete for infection sites and resources. Signup and view all the answers

What role do changes in root exudates play in the relationship between AM fungi and pathogens?

They can directly impact microbial pathogens. Signup and view all the answers

Which effect of AM fungi has been observed regarding pathogenic oomycetes?

They cause the exclusion of oomycetes from arbusculated cells. Signup and view all the answers

Which of the following is NOT a result of AM fungal influence on plants?

Inhibition of root growth Signup and view all the answers

What is the phenomenon called that results in the plant being in an 'alert' state, enhancing its response to attacks?

Priming Signup and view all the answers

Which hormone is reported to play a central role in the functioning of arbuscular mycorrhizal (AM) symbiosis?

Jasmonic acid Signup and view all the answers

How do AM fungi likely promote successful colonization of host plants?

By evading and manipulating the host immune system Signup and view all the answers

What is the main purpose of the autoregulation of symbiosis in plants?

To prevent excessive colonization and carbon drainage Signup and view all the answers

Which of the following describes the relationship between salicylic acid (SA) and jasmonic acid (JA) in mycorrhizal plants?

JA and SA act antagonistically in defense regulation Signup and view all the answers

What occurs during the early stages of interaction between AM fungi and host plants?

Transient increase of defense-related compounds Signup and view all the answers

What beneficial effect does priming provide to plants regarding pathogen attacks?

More efficient expression of basal defense mechanisms Signup and view all the answers

What type of plants tend to be more resistant to necrotrophs as a result of AM fungi interaction?

Plants that exhibit high levels of JA-dependent defenses Signup and view all the answers

In what way does the plant's defense mechanism change as a result of AM fungal colonization?

Defense signals such as SA and JA are altered. Signup and view all the answers

What are some of the consequences of the primed state in plants as influenced by AM fungi?

Faster and stronger defense responses upon re-exposure to pathogens Signup and view all the answers

Study Notes

Mechanisms of AM Fungi in Plant Protection

AM fungi protect plants against biotic stresses through direct competition and indirect, plant-mediated effects.
Direct effects involve competition for resources like carbon, nitrogen, and infection sites, reducing pathogenic fungi abundance in roots.
Pathogenic fungi and AM fungi exploit common resources, leading to negative correlations between their structures in roots and soil.
Root colonization by AM fungi alters root system architecture, morphology, and exudates, impacting pathogen dynamics and microbial community favorability.

Changes Induced by AM Fungi

Root exudation modifications affect microbial pathogens and nematodes directly.
AM fungi can reprogram plant gene expression, influencing plant primary and secondary metabolism related to defense.
Initial colonization by AM fungi activates plant defense responses, which may be suppressed for successful symbiosis, leading to a state known as priming.
Priming enhances plant defenses, resulting in faster and stronger responses to subsequent attacks, improving plant fitness and resistance.

Modulation of Host Plant's Immune System

AM fungi are recognized as alien organisms, prompting the plant's immune response which must be managed for successful colonization.
Plants maintain a feedback system to prevent excessive AM fungal colonization, termed autoregulation of the symbiosis.
Initial immune responses, including a transient increase in salicylic acid and defensive compounds, are limited compared to pathogen interactions.
AM fungi secrete effector proteins that may suppress plant defenses, facilitating colonization while modulating defense pathways.

Induced Systemic Resistance (ISR)

Mycorrhizal plants exhibit broad-spectrum resistance against various pathogens and herbivores, influenced by alterations in jasmonic acid and salicylic acid levels.
Resistance to necrotrophic and chewing insects correlates with increased JA-dependent defenses, while biotrophs target SA-regulated defenses.
Effective control of JA and SA signaling pathways is key for the protective benefits conferred by mycorrhizal associations.

Priming for Enhanced Defense

AM fungi induce resistance without direct activation of defense mechanisms, leading to tissue sensitization for efficient response upon pathogen attack.
Primed states involve moderate accumulation of regulatory molecules, such as transcription factors and MAP kinases.
Mycorrhizal roots display stronger defense mechanisms against pathogens like Fusarium and Phytophthora, including specific structural and biochemical responses.
AM fungi's priming effects extend beyond roots, enhancing defenses in aboveground tissues, demonstrated in studies of tomato plants against Botrytis cinerea.

Practical Implications

Understanding the interactions between AM fungi and plant defenses provides insights into ecological benefits and potential agricultural applications.
Research indicates that AM fungi can improve crop resistance, thereby enhancing productivity and reducing the need for chemical pesticides.

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Description

Explore the mechanisms through which arbuscular mycorrhizal (AM) fungi protect plants against biotic stresses. This quiz covers direct competition for resources, root colonization effects, and the reprogramming of plant gene expression. Understand how these interactions influence pathogen dynamics and enhance plant defense mechanisms.