The Symbiotic Bacteria—Xenorhabdus nematophila All and Photorhabdus luminescens H06 Strongly Affected the Phenoloxidase Activation of Nipa Palm Hispid, Octodonta nipae (Coleoptera: Chrysomelidae) Larvae

Abstract

Symbiotic bacteria form a mutualistic relationship with nematodes and are pathogenic to many insect pests. They kill insects using various strategies to evade or suppress their humoral and cellular immunity. Here we evaluate the toxic effects of these bacteria and their secondary metabolites on the survival and phenoloxidase (PO) activation of Octodonta nipae larvae using biochemical and molecular methods. The results show P. luminescens H06 and X. nematophila All treatments caused significant reductions in the number of O. nipae larvae in a dose-dependent manner. Secondly, the O. nipae immune system recognizes symbiotic bacteria at early and late stages of infection via the induction of C-type lectin. Live symbiotic bacteria significantly inhibit PO activity in O. nipae whereas heat-treated bacteria strongly increase PO activity. Additionally, expression levels of four O. nipae proPhenoloxidase genes following treatment with P. luminescens H06 and X. nematophila All were compared. We found that the expression levels of all proPhenoloxidase genes were significantly down-regulated at all-time points. Similarly, treatments of O. nipae larvae with metabolites benzylideneacetone and oxindole significantly down-regulated the expression of the PPO gene and inhibited PO activity. However, the addition of arachidonic acid to metabolite-treated larvae restored the expression level of the PPO gene and increased PO activity. Our results provide new insight into the roles of symbiotic bacteria in countering the insect phenoloxidase activation system.

Synergistic Insecticidal Effect of Photorhabdus luminescens and Bacillus thuringiensis against Fall Armyworm (Spodoptera frugiperda)

“…Then, by measuring the activity of melanization-related phenoloxidase in the hemolymph of S. frugiperda after treatment with Pl and by measuring the levels of reactive oxygen species (ROSs), which are important molecules in intracellular signaling and innate immune defense in insects, the immune inhibitory response induced by Pl can be assessed. This will help in understanding whether the two strains of Pl have different effects on inhibiting insects' immune responses [26,28,29].…”

“…Injection of a culture of P. luminescens H06 and the bacterial secondary metabolite benzylideneacetone (BZA) into Octodonta nipae inhibited the activity of phospholipase A2 (PLA2), which is necessary for the production of arachidonic acid (AA), an essential immune precursor of the eicosanoid class derived from AA. This also reduced the enzymatic activity of phenoloxidase (PO), effectively suppressing both cellular and humoral immune responses in insects [29]. However, potential barriers to the development of new microbial formulations include (1) difficulties in large-scale production, (2) high production costs, (3) environmental tolerance (temperature, humidity, UV light), and (4) short shelf life [66].…”

Molecular Identification of stink bug (Pentatomidae sp. BD39) and pod sucking bug (Mirperus sp.) associated with crops under rotation

“…However, various schemes had been put in place such as medium to large irrigation schemes; FADAMA projects to further boost agricultural production and meet population growth. Several challenges of this agriculture intensi cations to avert the threat in food security in Nigeria includes Soil salinity, decreasing soil and water quality and loss of vegetation and build of up pests and diseases [1,2,3,4,5,6]. Pests and diseases problems in the farms leads to widespread application of chemicals which cause serious cases of poisoning, contamination of the environment and even the increased resistance of pests to the active substances.…”