56
purpose of this study is to present the siderophore biosynthesis pathways in
Monilinia spp. causing brown rot in stone fruits focusing on the siderophore production along with their uptake and utilization mechanisms and represent an ideal
target for pathogen-specific, host friendly therapeutic strategy, which would block
the proliferation of fungus without causing any harm to the host. This study comprehensively compiles the information currently available to better understand siderophore biosynthesis pathways in Monilinia spp. related to BR resistance.
4.3 Pathways of Fungal Siderophores Biosynthesis
The progress in the knowledge of the novel targets of the siderophores biosynthesis
path has undergone great progress in recent years; there is a substantial contradiction between the information provided by the considerable number of wellcharacterized biosynthetic pathways of siderophores. The mechanisms are
potentially attractive objectives with respect to the control of pathogens.
The siderophore biosynthesis starts from precursors such as citrate, amino acids,
dihydroxybenzoate, and N
5
-acyl-N
5
-hydroxioritine. Some genes have been
described for the secretion of siderophores in bacteria and fungi that also have
homologous genes in other microbial species. The siderophores are produced and
assembled from non-ribosomal cytoplasm synthase. In general, the biosynthesis
pathways of siderophore can be differentiated as being either dependent on or independent of an enzyme NRPSs (non-ribosomal peptide synthetases). In this section,
the biosynthesis of siderophores will be discussed as aspects of secretion, absorption, and release of iron siderophores.
There are two main pathways for siderophores biosynthesis:
4.3.1 Non-Ribosomal Peptide Synthetases (NRPSs) Multi
Enzymes Dependent
Nonribosomal peptide synthetase (NRPS) enzyme complexes synthesize nonribosomal peptides are called modular multidomain enzymes. Nonmodular NRPS
enzymes are found in siderophores biosynthetic pathway like EntE and VibH in
enterobactin, and VibE in vibriobactin.
4.3.2 NRPS-Independent
Non- ribosomal peptides (NRPs) are synthesized by a large multimodular enzymes
NRPSs in which each module are associated for the incorporation of an amino acid
into the peptide chain. Generally, the number and order of the modules determine the
number and order of the amino acids in the peptide product (Crosa and Walsh 2002).
Characteristic for NRPSs are the core domains for adenylation, thiolation, and condensation. The activation domain (A) of each module of the NRPS recognizes and
S. Ashraf et al.
purpose of this study is to present the siderophore biosynthesis pathways in
Monilinia spp. causing brown rot in stone fruits focusing on the siderophore production along with their uptake and utilization mechanisms and represent an ideal
target for pathogen-specific, host friendly therapeutic strategy, which would block
the proliferation of fungus without causing any harm to the host. This study comprehensively compiles the information currently available to better understand siderophore biosynthesis pathways in Monilinia spp. related to BR resistance.
4.3 Pathways of Fungal Siderophores Biosynthesis
The progress in the knowledge of the novel targets of the siderophores biosynthesis
path has undergone great progress in recent years; there is a substantial contradiction between the information provided by the considerable number of wellcharacterized biosynthetic pathways of siderophores. The mechanisms are
potentially attractive objectives with respect to the control of pathogens.
The siderophore biosynthesis starts from precursors such as citrate, amino acids,
dihydroxybenzoate, and N
5
-acyl-N
5
-hydroxioritine. Some genes have been
described for the secretion of siderophores in bacteria and fungi that also have
homologous genes in other microbial species. The siderophores are produced and
assembled from non-ribosomal cytoplasm synthase. In general, the biosynthesis
pathways of siderophore can be differentiated as being either dependent on or independent of an enzyme NRPSs (non-ribosomal peptide synthetases). In this section,
the biosynthesis of siderophores will be discussed as aspects of secretion, absorption, and release of iron siderophores.
There are two main pathways for siderophores biosynthesis:
4.3.1 Non-Ribosomal Peptide Synthetases (NRPSs) Multi
Enzymes Dependent
Nonribosomal peptide synthetase (NRPS) enzyme complexes synthesize nonribosomal peptides are called modular multidomain enzymes. Nonmodular NRPS
enzymes are found in siderophores biosynthetic pathway like EntE and VibH in
enterobactin, and VibE in vibriobactin.
4.3.2 NRPS-Independent
Non- ribosomal peptides (NRPs) are synthesized by a large multimodular enzymes
NRPSs in which each module are associated for the incorporation of an amino acid
into the peptide chain. Generally, the number and order of the modules determine the
number and order of the amino acids in the peptide product (Crosa and Walsh 2002).
Characteristic for NRPSs are the core domains for adenylation, thiolation, and condensation. The activation domain (A) of each module of the NRPS recognizes and
S. Ashraf et al.