144
while NPS2 is responsible for the intracellular siderophore production and on gene
deletion impairing the sexual spore production. The deletion of NPS6 gene rendered
sensitivity to iron starvation, oxidative stress, and reduced virulence. Both NPS1
and NPS6 are responsible for extracellular siderophore production among which
NPS1 accounts for the synthesis of malonichrome (a ferrichrome- type siderophore
compound) in F. graminearum. The triple mutant (nps1nps2nps6) strain of F. graminearum lacks all three siderophores and demonstrated damage in all the attributes
such as spore production, iron sequestration, ROS, and virulence factor (Oide
et al. 2015).
In A. fumigatus hydroxamates fusarinine C and triacetylfusarinine C serve in
capturing extracellular iron, ferricrocin for distribution of iron within the cell and
hyphal storage, hydroxyferricrocin for iron conidial storage, germination, and oxidative stress resistance (Khan et al. 2017). The biosynthesis pathway for triacetylfusarinine, ferricrocin, and hydroxyferricrocin of A. fumigatus was schematically
represented by Khan et al. (2017) and also includes the catecholate siderophore
mapping from the KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway
database.
The impact of fungal siderophores on the fungal sexual development was
observed when the fungus lacks the siderophore ferricrocin storage resulting in the
formation of deprived ascospore development in strains of Cochliobolus heterostrophus (Oide et al. 2007) and affecting asexual sporulation in Aspergillus fumigatus
and Magnaporthe grisea (Hof et al. 2009; Schrettl et al. 2007). This postulates that
siderophores might be involved in delivering iron at the appropriate time (Oide
et al. 2007).
Intriguingly, Forester et al. (2017) studied the functions of the genes SidN, SidC,
and SidA in the symbiotic, endophytic fungi Epichloe festucae with host ryegrass
(Lolium perenne), indicated SidA gene encodes the precursor, ornithine N
5
- monooxygenase is responsible for the production of epichloenin and ferricrocin, which
are encoded by SidN and SidC, respectively. Also studies on genes and gene mutation clearly depicted the contrasting functions of intracellular and extracellular siderophores in maintaining the iron homeostasis. Furthermore, the cellular energy
uptake for the siderophore biosynthesis is remarkably high in microbes; hence to
sustain the situation, a tight regulation might be followed under significant iron
shortage (Oberegger et al. 2001).
The vision on fungal siderophores has been increased in the recent decades;
therefore this chapter comprises the applications and advancements in siderophore
studies in fungal species (Fig. 9.2).
9.4 Applications of Fungal Siderophores
Fungal siderophores have vast application in the field of agriculture, environment,
and health care.
S. Manoharan et al.
while NPS2 is responsible for the intracellular siderophore production and on gene
deletion impairing the sexual spore production. The deletion of NPS6 gene rendered
sensitivity to iron starvation, oxidative stress, and reduced virulence. Both NPS1
and NPS6 are responsible for extracellular siderophore production among which
NPS1 accounts for the synthesis of malonichrome (a ferrichrome- type siderophore
compound) in F. graminearum. The triple mutant (nps1nps2nps6) strain of F. graminearum lacks all three siderophores and demonstrated damage in all the attributes
such as spore production, iron sequestration, ROS, and virulence factor (Oide
et al. 2015).
In A. fumigatus hydroxamates fusarinine C and triacetylfusarinine C serve in
capturing extracellular iron, ferricrocin for distribution of iron within the cell and
hyphal storage, hydroxyferricrocin for iron conidial storage, germination, and oxidative stress resistance (Khan et al. 2017). The biosynthesis pathway for triacetylfusarinine, ferricrocin, and hydroxyferricrocin of A. fumigatus was schematically
represented by Khan et al. (2017) and also includes the catecholate siderophore
mapping from the KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway
database.
The impact of fungal siderophores on the fungal sexual development was
observed when the fungus lacks the siderophore ferricrocin storage resulting in the
formation of deprived ascospore development in strains of Cochliobolus heterostrophus (Oide et al. 2007) and affecting asexual sporulation in Aspergillus fumigatus
and Magnaporthe grisea (Hof et al. 2009; Schrettl et al. 2007). This postulates that
siderophores might be involved in delivering iron at the appropriate time (Oide
et al. 2007).
Intriguingly, Forester et al. (2017) studied the functions of the genes SidN, SidC,
and SidA in the symbiotic, endophytic fungi Epichloe festucae with host ryegrass
(Lolium perenne), indicated SidA gene encodes the precursor, ornithine N
5
- monooxygenase is responsible for the production of epichloenin and ferricrocin, which
are encoded by SidN and SidC, respectively. Also studies on genes and gene mutation clearly depicted the contrasting functions of intracellular and extracellular siderophores in maintaining the iron homeostasis. Furthermore, the cellular energy
uptake for the siderophore biosynthesis is remarkably high in microbes; hence to
sustain the situation, a tight regulation might be followed under significant iron
shortage (Oberegger et al. 2001).
The vision on fungal siderophores has been increased in the recent decades;
therefore this chapter comprises the applications and advancements in siderophore
studies in fungal species (Fig. 9.2).
9.4 Applications of Fungal Siderophores
Fungal siderophores have vast application in the field of agriculture, environment,
and health care.
S. Manoharan et al.