59
recently, it has been reported that NPS2/SidC is responsible for the biosynthesis of
ferricrocin in F. graminearum. Based on the analysis of gene expression, protein
identification, and siderophore detection, we hypothesized that NRP synthesizes
sidC, D, and E, potentially biosynthesis the siderophores responsible for iron acquisition in Monilinia spp. although direct proof of this remains outstanding. Thus,
although advances in NRPS are emerging, further work is urgently required to fully
elucidate the nature of this important process, in particular, adenylation domain specificity and NRP product identification and function.
4.4 Siderophores and Plant Immune Responses
Plants are exposed to various biotic stresses; therefore they have developed a wide
range of endogenous defense mechanisms against potential plant pathogens. In
addition to preformed physical and chemical barriers, plants can detect attacks of
pathogens and activate various complex signaling cascades, which lead to induced
resistance against pathogens. Induced innate immune responses include phosphorylation processes, accumulation of reactive oxygen species (ROS), cell wall rigidification and degradation of biomolecules, deposition of the callose, defense hormonal
signaling, and expression of pathogenesis-related (PR) gene encoding pathogenesis
(Nurnberger et al. 2004).
To activate these defenses against potential microbial pathogens, the plants are
equipped with a complex sentinel system comprising proteins dedicated to the recognition of inducers received from pathogens. Recognition of preserved motifs in
microbial molecules called microbe-associated molecular patterns (MAMP)
requires membrane-anchored pattern recognition receptors (PRRs). At the time of
infection, components such as oligo-galacturonide or the peptides are released from
the plant cells and are called damage-associated molecular patterns (DAMPs). It
can be recognized by specific PRRs and activated defense mechanisms. Plants also
contribute a complex recognition system associated with resistance proteins that
directly or indirectly allow recognition of proteins secreted by pathogens, known as
effectors, with reference to the fact that these proteins are attributed to the promotion of infections (Nurnberger et al. 2004).
More recently, Albarouki et al. (2014) demonstrated that secretion of coprogens
from the hemibiotrophic fungus C. graminicola on maize activate defense responses.
Interestingly, genes associated with coprogen biosynthesis are suppressed during
the first biotrophic phase of invasion and are upregulated during the necrotrophic
phase. Thus, the fungus tightly controls the production of siderophores at the early
stages of infection probably to avoid the plant’s immune system.
To understand the molecular mechanisms associated with immunity mediated by
siderophores in leaves better, the plant immune system triggered by siderophores in
A. thaliana has been extinsevely studied.
4 Siderophores: Mediated Iron Acquisition and Virulence of Brown Rot Disease…
recently, it has been reported that NPS2/SidC is responsible for the biosynthesis of
ferricrocin in F. graminearum. Based on the analysis of gene expression, protein
identification, and siderophore detection, we hypothesized that NRP synthesizes
sidC, D, and E, potentially biosynthesis the siderophores responsible for iron acquisition in Monilinia spp. although direct proof of this remains outstanding. Thus,
although advances in NRPS are emerging, further work is urgently required to fully
elucidate the nature of this important process, in particular, adenylation domain specificity and NRP product identification and function.
4.4 Siderophores and Plant Immune Responses
Plants are exposed to various biotic stresses; therefore they have developed a wide
range of endogenous defense mechanisms against potential plant pathogens. In
addition to preformed physical and chemical barriers, plants can detect attacks of
pathogens and activate various complex signaling cascades, which lead to induced
resistance against pathogens. Induced innate immune responses include phosphorylation processes, accumulation of reactive oxygen species (ROS), cell wall rigidification and degradation of biomolecules, deposition of the callose, defense hormonal
signaling, and expression of pathogenesis-related (PR) gene encoding pathogenesis
(Nurnberger et al. 2004).
To activate these defenses against potential microbial pathogens, the plants are
equipped with a complex sentinel system comprising proteins dedicated to the recognition of inducers received from pathogens. Recognition of preserved motifs in
microbial molecules called microbe-associated molecular patterns (MAMP)
requires membrane-anchored pattern recognition receptors (PRRs). At the time of
infection, components such as oligo-galacturonide or the peptides are released from
the plant cells and are called damage-associated molecular patterns (DAMPs). It
can be recognized by specific PRRs and activated defense mechanisms. Plants also
contribute a complex recognition system associated with resistance proteins that
directly or indirectly allow recognition of proteins secreted by pathogens, known as
effectors, with reference to the fact that these proteins are attributed to the promotion of infections (Nurnberger et al. 2004).
More recently, Albarouki et al. (2014) demonstrated that secretion of coprogens
from the hemibiotrophic fungus C. graminicola on maize activate defense responses.
Interestingly, genes associated with coprogen biosynthesis are suppressed during
the first biotrophic phase of invasion and are upregulated during the necrotrophic
phase. Thus, the fungus tightly controls the production of siderophores at the early
stages of infection probably to avoid the plant’s immune system.
To understand the molecular mechanisms associated with immunity mediated by
siderophores in leaves better, the plant immune system triggered by siderophores in
A. thaliana has been extinsevely studied.
4 Siderophores: Mediated Iron Acquisition and Virulence of Brown Rot Disease…