53
To avoid iron deficiency, many plants rely on excretion mechanisms of phytosiderophores (i.e., chelated compounds, common in iron-sequestering herbs) from the
roots and the secretion of siderophores by a group of microbes to facilitate absorption of the Fe complex under iron deficiency, for maintaining iron homeostasis by
controlling the absorption. Use and storage of iron depends on its environmental
availability (Neilands 1995). Although iron is one of the most abundant elements on
earth, bioavailability is lower in aerobic conditions (in the presence of oxygen and
neutral pH), mainly because ferric iron (concomitant oxidation of Fe
2+
to Fe
3+
)
reacts with oxygen to form insoluble ferric hydro-oxide.
Pathogenic fungi of the genus Monilinia spp. includes numerous aggressive and
economically important pathogens of the Rosaceae, Ericaceae, and Empetraceae.
They are distributed all over the world and are one of the most limiting factors for
the production stone and pome fruits, and also berries all over the world. These
pathogens are often referred to as “brown rot” agents. The host range of Monilinia
spp. includes apple, pear, quince, cherry, apricot, plum, peach, nectarine, almond, etc.
Four species of Monilinia spp. are considered economically significant: M. fructicola, M. laxa, M. fructigena, and M. polystroma are known pathogens that influence rosaceous fruit production worldwide. Other species such as M. oxycocci,
M. baccarum, M. urnula, and M. vaccinii-corymbosi inhabit the Vaccinium host
especially in North America. M. fructicola is identified in America, Australia, and
New Zealand. It has been reported for the first time in French peach orchards and
then in Spain (Garcia- Benitez et al. 2016), Switzerland (Bosshard et al. 2006),
Hungary (Petróczy and Palkovics 2009), and Italy (Pellegrino et al. 2009) on
peaches.
Monilinia spp. are economically important pathogens, very difficult to control.
In this paper we have highlighted the metabolic pathways; specifically siderophore
biosynthesis, uptake and utilization, triggered in the Monilinia spp. in iron starving
conditions and further importance of siderophores can interfere with the action of
the Monilinia spp. because they may inhibit enzymes important for their installation
in the wounds post-harvest infection of brown rot of stone fruit.
4.2 Siderophore and Fungal Pathogenesis
Siderophores are specific chelators of ferric iron of low affinity and low molecular
weight (<10 kDa). Siderophores are secreted by all prokaryotic and eukaryotic microorganisms, except Saccharomyces cerevisiae, Candida albicans, and Cryptococcus
neoformans. Those who cannot produce siderophores can use siderophores produced
by other microorganisms, called xenosideróforos. The microorganisms secrete one or
more siderophores through specific receptors on the surface of the cells depending on
the type and severity of the deficiency. Its biosynthesis is controlled by the availability
of iron and produced by bacteria, fungi, and plants in limited iron conditions to stimulate plant growth to extract iron from the environment and make the mineral available
for the cell near the root (Ahmed and Holmström 2014). In fungi, there are extracel4 Siderophores: Mediated Iron Acquisition and Virulence of Brown Rot Disease…
To avoid iron deficiency, many plants rely on excretion mechanisms of phytosiderophores (i.e., chelated compounds, common in iron-sequestering herbs) from the
roots and the secretion of siderophores by a group of microbes to facilitate absorption of the Fe complex under iron deficiency, for maintaining iron homeostasis by
controlling the absorption. Use and storage of iron depends on its environmental
availability (Neilands 1995). Although iron is one of the most abundant elements on
earth, bioavailability is lower in aerobic conditions (in the presence of oxygen and
neutral pH), mainly because ferric iron (concomitant oxidation of Fe
2+
to Fe
3+
)
reacts with oxygen to form insoluble ferric hydro-oxide.
Pathogenic fungi of the genus Monilinia spp. includes numerous aggressive and
economically important pathogens of the Rosaceae, Ericaceae, and Empetraceae.
They are distributed all over the world and are one of the most limiting factors for
the production stone and pome fruits, and also berries all over the world. These
pathogens are often referred to as “brown rot” agents. The host range of Monilinia
spp. includes apple, pear, quince, cherry, apricot, plum, peach, nectarine, almond, etc.
Four species of Monilinia spp. are considered economically significant: M. fructicola, M. laxa, M. fructigena, and M. polystroma are known pathogens that influence rosaceous fruit production worldwide. Other species such as M. oxycocci,
M. baccarum, M. urnula, and M. vaccinii-corymbosi inhabit the Vaccinium host
especially in North America. M. fructicola is identified in America, Australia, and
New Zealand. It has been reported for the first time in French peach orchards and
then in Spain (Garcia- Benitez et al. 2016), Switzerland (Bosshard et al. 2006),
Hungary (Petróczy and Palkovics 2009), and Italy (Pellegrino et al. 2009) on
peaches.
Monilinia spp. are economically important pathogens, very difficult to control.
In this paper we have highlighted the metabolic pathways; specifically siderophore
biosynthesis, uptake and utilization, triggered in the Monilinia spp. in iron starving
conditions and further importance of siderophores can interfere with the action of
the Monilinia spp. because they may inhibit enzymes important for their installation
in the wounds post-harvest infection of brown rot of stone fruit.
4.2 Siderophore and Fungal Pathogenesis
Siderophores are specific chelators of ferric iron of low affinity and low molecular
weight (<10 kDa). Siderophores are secreted by all prokaryotic and eukaryotic microorganisms, except Saccharomyces cerevisiae, Candida albicans, and Cryptococcus
neoformans. Those who cannot produce siderophores can use siderophores produced
by other microorganisms, called xenosideróforos. The microorganisms secrete one or
more siderophores through specific receptors on the surface of the cells depending on
the type and severity of the deficiency. Its biosynthesis is controlled by the availability
of iron and produced by bacteria, fungi, and plants in limited iron conditions to stimulate plant growth to extract iron from the environment and make the mineral available
for the cell near the root (Ahmed and Holmström 2014). In fungi, there are extracel4 Siderophores: Mediated Iron Acquisition and Virulence of Brown Rot Disease…