Adipokinetic Hormones Enhance the Efficacy of the Entomopathogenic Fungus Isaria fumosorosea in Model and Pest Insects

Abstract

Insect adipokinetic hormones (AKHs) are neuropeptides with a wide range of actions, including the control of insect energy metabolism. These hormones are also known to be involved in the insect defence system against toxins and pathogens. In this study, our aim was to demonstrate whether the application of external AKHs significantly enhances the efficacy of the entomopathogenic fungus Isaria fumosorosea in a model species (firebug Pyrrhocoris apterus) and pest species (Egyptian cotton leafworm Spodoptera littoralis and pea aphid Acyrthosiphon pisum). It was found that the co-application of Isaria with AKHs significantly enhanced insect mortality in comparison to the application of Isaria alone. The mode of action probably involves an increase in metabolism that is caused by AKHs (evidenced by the production of carbon dioxide), which accelerates the turnover of Isaria toxins produced into the infected insects. However, several species-specific differences probably exist. Intoxication by Isaria elicited the stimulation of Akh gene expression and synthesis of AKHs. Therefore, all interactions between Isaria and AKH actions as well as their impact on insect physiology from a theoretical and practical point of view need to be discussed further.

Nonlethal effects of predation: Presence of insectivorous birds affects the behaviour and level of stress in insects

“…For example, 20 minutes of forced running (in a horizontal laboratory shaker) resulted in a slight increase of AKH titre in the CNS of the firebug, Pyrrhocoris apterus, but in a strong increase of the titre in the haemolymph (Kodrík and Socha, 2005). A similar picture can be seen when applying various pathogens (Ibrahim et al, 2017;Ibrahim et al, 2018;Gautam et al, 2020a;Gautam et al, 2020b) or toxins including insecticides (Candy, 2002;Kodrík et al, 2015). Changes in the AKH levels in the haemolymph are often faster, while in the CNS are slower but more profound.…”

Influence of Asafoetida Extract on the Virulence of the Entomopathogenic Nematode Steinernema carpocapsae and Its Symbiotic Bacterium Xenorhabdus nematophila in the Host Pyrrhocoris apterus

“…They were supplied with linden seeds and water. Freshly ecdysed adults were transferred to small 0.25 L glass jars (females and males separately) and kept under the same photoperiodic, food, and temperature regimes as those under which they had developed [ 22 ]. To have uniform materials, only 7-day-old males were used for the experiments.…”

What You Eat Matters: Nutrient Inputs Alter the Metabolism and Neuropeptide Expression in Egyptian Cotton Leaf Worm, Spodoptera littoralis (Lepidoptera: Noctuidae)

“…cDNA was synthesized from RNA using the iScript TM cDNA Synthesis Kit (Bio-Rad Laboratories Inc.) according to the instructions of the manufacturer and quantified using a CFX96 Touch TM Real-Time PCR Detection System (Bio-Rad Laboratories) and an SYBR Green qPCR kit (Bio-Rad Laboratories Inc.). Primers developed by Gautam et al (2020) were used for expression analysis of SpoliAKH , while primers to amplify transcripts from SpoliILP1 , SpoliILP2 , and SpolisNPF were designed using Primer3Plus software with the following parameters: product size = 70–180 bp, Tm = 59–61°C, GC% = 40–60%, Max Poly-base = 3 ( Table 1 ). Actin was used as the endogenous reference gene for normalizing gene transcript abundance ( Večeřa et al, 2012 ).…”