Expression and characterization of two chitinases with synergistic effect and antifungal activity from Xenorhabdus nematophila

Functional Comparison of Three Chitinases from Symbiotic Bacteria of Entomopathogenic Nematodes

“…Chitinases identified from various bacteria have insecticidal and antifungal activities. These pesticidal chitinases have been also identified from EPN symbiotic bacteria, Xenorhabdus and Photorhabdus [ 32 , 33 , 40 , 42 , 43 ]. Xenorhabdus and Photorhabdus, having insecticidal activity, exhibit different pathogenicity depending on the species or strain [ 37 , 39 ].…”

“…In particular, XnChi is relatively close to the X. nematophila ATCC19061 chitinase (Genbank accession number: WP 010846090.1), which shows 99.69% homology to Chi70 (Genbank accession number: GK44779.1) of X. nematophila . Chi70 was reported to have insecticidal and antifungal activities against certain pests and fungi, and to improve insecticidal activity of BtCryAc and Tc toxins [ 23 , 31 , 32 ]. Thus, symbiotic bacterial chitinases of EPNs could be promising control agents of insect pests and plant pathogenic fungi by playing an important role in pesticidal activity.…”

“…The result is assumed to be consistent with previous research, which reported that the combination of endochitinase and chitobiosidase showed higher antifungal activity [ 58 ]. In fact, antifungal activity of chitinases from symbiotic bacteria of EPN has been reported in several studies [ 32 , 33 ]. For example, the partially purified chitinase enzyme from X. bovienii has exhibited strong antifungal activity against Botrytis cinerea by inhibiting conidial germination and germ tube elongation or lysing the germ tube [ 54 ].…”

“…In addition, two chitinase (chi60 and chi70) genes were found in the toxin complex locus of X. nematophila [ 31 ] and the corresponding proteins were shown to be vital for the insecticidal activity against Helicoverpa armigera in the toxicity of Tc toxins [ 23 ]. Moreover, chitinases are able to inhibit the elongation and growth of mycelia and spore germination of fungi [ 32 ], that is, chitinase Chi2A and chitin binding protein (CBP) in the secondary cells of P. luminescens are necessary to inhibit the growth of Fusarium graminearum [ 33 ]. Thus, chitinases could be potential and effective virulence factors for the biological control of insect pests and plant pathogenic fungi.…”

“…This suggests the possibility that even the same pathogenic protein may have different biological activities, e.g., due to amino acid variability. Accordingly, chitinases are important toxic and antifungal factors against insect larvae and plant pathogenic fungi [ 32 , 33 , 40 ]; nevertheless, symbiotic bacterial chitnases of EPNs have not been studied except X . nematophila and P .…”