Genomic insight into the insecticidal potential of a new Pseudomonas chlororaphis isolate

Pseudomonas fluorescens group, such as Pseudomonas protegens and Pseudomonas chlororaphis, can be utilized as insect-killing agents. Most insecticidal Pseudomonas described so far have high toxicity for insects of the order Lepidoptera. In this study, Pseudomonas strain PcR3-3 was isolated from the willow root. It showed a high mortality for the coleopteran species Plagiodera versicolora (Coleoptera: Chrysomelidae), but not for the lepidopteran Helicoverpa armigera. Strain PcR3-3 displayed high colonization ability in the P. versicolora compared with P. chlororaphis PCL1391, indicating that the insecticidal activities correlated with the colonization ability of Pseudomonas strain in the host. Phylogenetic analysis of the genome revealed that PcR3-3 belonged to P. chlororaphis subsp. aureofaciens. Numerous insecticidal protein-encoding genes, typical biosynthetic gene clusters for some insecticidal metabolite and type VI secretion system, known to be involved in insect pathogenicity, were present in the P. chlororaphis PcR3-3 genome. However, the insecticidal toxin Fit-encoding gene which commonly presents in P. chlororaphis, was not found in the P. chlororaphis PcR3-3 genome. Furthermore, there are some divergent insecticidal genes between P. chlororaphis PcR3-3 and P. chlororaphis PCL1391. This finding implies that P. chlororaphis PcR3-3 is a promising biocontrol agent for pest management applications. The P. chlororaphis-P. versicolora association can be used as a model system to study the interaction between Pseudomonas and coleopteran insects.