The chitinase C gene PsChiC from Pseudomonas sp. and its synergistic effects on larvicidal activity

Abstract

Pseudomonas sp. strain TXG6-1, a chitinolytic gram-negative bacterium, was isolated from a vegetable field in Taixing city, Jiangsu Province, China. In this study, a Pseudomonas chitinase C gene (PsChiC) was isolated from the chromosomal DNA of this bacterium using a pair of specific primers. The PsChiC gene consisted of an open reading frame of 1443 nucleotides and encoded 480 amino acid residues with a calculated molecular mass of 51.66 kDa. The deduced PsChiC amino acid sequence lacked a signal sequence and consisted of a glycoside hydrolase family 18 catalytic domain responsible for chitinase activity, a fibronectin type III-like domain (FLD) and a C-terminal chitin-binding domain (ChBD). The amino acid sequence of PsChiCshowed high sequence homology (> 95%) with chitinase C from Serratia marcescens. SDS-PAGE showed that the molecular mass of chitinase PsChiC was 52 kDa. Chitinase assays revealed that the chitobiosidase and endochitinase activities of PsChiCwere 51.6- and 84.1-fold higher than those of pET30a, respectively. Although PsChiC showed little insecticidal activity towards Spodoptera litura larvae, an insecticidal assay indicated that PsChiC increased the insecticidal toxicity of SpltNPV by 1.78-fold at 192 h and hastened death. These results suggest that PsChiC from Pseudomonas sp. could be useful in improving the pathogenicity of baculoviruses.

Lethal and Sublethal Effects of Three Microbial Biocontrol Agents on Spodoptera litura and Its Natural Predator Rhynocoris kumarii

“…The Spodoptera -specific virus SpltNPV has been applied to suppress the pest populations in many countries [ 23 , 24 ]. Also, SpltNPV and a Pseudomonas chitinase C gene ( PsChiC ) caused 51.1% and 17.8% mortality against second instar larvae of S. litura after 196 h, respectively [ 52 ]. In contrast, our results revealed higher mortality of S. litura third instar larvae in SpltNPV (62.9%) and P. fluorescens (38.4%) treatments even at 96 h, which could have occurred due to the differences in the selected age group of the pest population.…”

“…Recently, a Pseudomonas sp. (TXG6-1) chitinase C gene (PsChiC) was introduced for the management of S. litura (1 × 10 7 particles) [ 52 ]. In addition to the use of Pseudomonas as an alternative EPM, various strains of M. anisopliae applied at 10 8 conidia/mL caused 67% mortality to S. litura for third instar larvae [ 52 ].…”

Serratia marcescenssecretes proteases and chitinases with larvicidal activity againstAnopheles dirus

“…marcescens (Aggarwal et al, 2015;Binod et al, 2007). However, many studies suggested that chitinases might not be ideal to be used as a stand-alone insecticide for some insects because the larvicidal activity from chitinase can be marginal (Bahar et al, 2012;Zhong et al, 2015). Rather, the enzymes could be used to enhance the insecticidal activity of other control agents including Bt toxin, entomopathogenic virus and chemical insecticides (Kelkenberg et al, 2015;Ramírez-Suero et al, 2011;Zhong et al, 2015).…”

Chitinases of Bacillus thuringiensis: Phylogeny, Modular Structure, and Applied Potentials

“…There is evidence to suggest that the CBD affects how the enzyme accesses glycosidic bonds within chitin strands (Svitil and Kirchman, 1998). Aromatic amino acids (W, Y) in the CBD are highly conserved and appear to be essential for hydrophobic binding with the pyranosyl rings of N-acetylglucosamine residues in chitin (Zhong et al, 2015). In particular for ChiA74 the CBD belongs to the carbohydratebinding type 2 domain subfamily b (CBM2b).…”