Intermittent food shortages are commonly encountered in the wild. During winter or starvation stress, mammals often choose to hibernate while insects—in the form of eggs, mature larvae, pupae, or adults opt to enter diapause. In response to food shortages, insects may try to find sufficient food to maintain normal growth and metabolism through distribution of populations or even migration. In the face of hunger or starvation, insect responses can include changes in behavior and/or maintenance of a low metabolic rate through physiological adaptations or regulation. For instance, in order to maintain homeostasis of the blood sugar, trehalose under starvation stress, other sugars can be transformed to sustain basic energy metabolism. Furthermore, as the severity of starvation increases, lipids (especially triglycerides) are broken down to improve hunger resistance. Starvation stress simultaneously initiates a series of neural signals and hormone regulation processes in insects. These processes involve neurons or neuropeptides, immunity-related genes, levels of autophagy, heat shock proteins and juvenile hormone levels which maintain lower levels of physiological metabolic activity. This work focuses on hunger stress in insects and reviews its effects on behavior, energy reserve utilization, and physiological regulation. In summary, we highlight the diversity in adaptive strategies of insects to hunger stress and provides potential ideas to improve hunger resistance and cold storage development of natural enemy insects. This gist of literature on insects also broadens our understanding of the factors that dictate phenotypic plasticity in adjusting development and life histories around nutritionally optimal environmental conditions.

Akirin is an essential nuclear protein involved in the regulation of NF-κB signaling pathway. In most invertebrates, Akirin regulates NF-κB-related Imd and Toll pathways, however, in Drosophila, it only controls the Imd pathway, whereas its role in NF-κB signaling pathway in other insect species is unclear. In the present study, we used white-backed planthopper Sogatella furcifera as a model to investigate the functional activity of Akirin in insects. The sequence of Akirin cDNA was extracted from transcriptome database of S. furcifera; it contained a 585 bp open reading frame (ORF) encoding a putative protein of 194 amino acids. S. furcifera Akirin (SfAkirin) had a molecular weight of about 21.69 kDa and a theoretical pI of 8.66 and included a nuclear localization signal (NLS) of five amino acid residues at the N-terminal region. Evolutionary analysis showed that SfAkirin was evolutionary closer to Akirins of such relatively distant species as crustaceans than to those of some insect orders like Diptera and Hymenoptera. Tissue-specific expression analysis showed that the SfAkirin gene was expressed in all examined tissues, with the highest expression levels detected in the testis, followed by the ovary, whereas the lowest expression was found in the head. Real-time quantitative PCR analysis showed that SfAkirin mRNA was strongly induced in response to injection of heat-inactivated Escherichia coli and Bacillus subtilis, whereas SfAkirin silencing by RNA interference significantly reduced the expression of NF-κB dependent transcription factors Dorsal and Relish after B. subtilis and E. coli challenge, respectively. Our results suggest that SfAkirin may control the immune response of S. furcifera against bacterial infection via both Imd and Toll signaling pathways.

Concentrations of Cu, Zn, Fe, Mn, Pb, Cd, As, and Hg were analyzed in the surface water and muscle of seven fish species (Carassius auratus, Cyprinus carpio, Hemiculter leucisculus, Pelteobagrus fulvidraco, Silurus meriaionalis, Ctenopharyngodon idellus, and Parabramis pekinensis) from the Wujiangdu reservoir, China. All metal concen-trations in water were lower than grade one water quality values. Mean metal concentrations in the fish muscle decreased in the order: Zn (10.765 mg kg−1) > Fe (8.908 mg kg−1) > Mn (0.373 mg kg−1) > Cu (0.369 mg kg−1) > Pb (0.158 mg kg−1) > As (0.102 mg kg−1) > Hg (0.042 mg kg−1) > Cd (0.024 mg kg−1). Metal concentrations were higher in omnivorous and carnivorous fish than those in herbivorous fish. The bioconcentration factor (BCF) of Hg was much higher than that of other metals in all fish species. The values of target hazard quotient (THQ) and hazard index (HI) were lower than 1 for fishermen and the general population, indicating that there was no considerable noncarcinogenic risk. However, target cancer risk (TR) values were greater than 1.0 × 10−6, indicating that the car-cinogenic risk caused by fish consumption could not be ignored. Several kinds of fish species were not completely safe for human consumption according to the standard of the European Commission. The potential health risks in fishermen were much higher than that in the general population.

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Cadmium (Cd) is absorbed and accumulated by crops, and it adversely affects plant growth and development. To explore the effect of exogenous auxin on Cd stress, we applied different concentrations of α-naphthaleneacetic acid (NAA) and the auxin transport inhibitor 2,3,5-triiodobenzoic acid (TIBA) to tomato plants exposed to Cd stress in a hydroponic system. NAA and TIBA at different concentrations were used under Cd stress. Plant growth, root morphology, and auxin distribution were observed. Lipid peroxidation and antioxidant enzyme activities in leaves, cadmiumcontent, and migration coefficient of plants were determined. Transcriptome sequencing and qRT-PCR were used to analyze the differentially expressed genes. Results showed that auxin was concentrated in the leaf veins, stem base, and roots in P5::GUS “Chico III” transgenic tomato, indicating NAA polar transport to the roots and promotion of root growth under Cd stress. Cd was absorbed by the roots and transported to the shoots. It then inhibited plant growth and promoted antioxidant enzyme activities, O2− production, H2O2 accumulation, and membrane lipid peroxidation. Treatment with 0.5 μM NAA improved antioxidant enzyme activities, reduced reactive oxygen, maintained membrane permeability, and decreased malondialdehyde and proline contents. Transcriptome analysis revealed that NAA activated a large number of genes in the roots: 1998 genes were differentially expressed in response to Cd or NAA treatment, and 1736 genes were specifically expressed in response to NAA treatment under Cd stress. Among the differentially expressed genes, tomato metallocarboxypeptidase inhibitor TCMP-2 (2A11) and Solanum lycopersicum heavy metal-associated isoprenylated plant protein (HIPP) 7-like (LOC101264884), which are closely related to plant response to heavy metal stress, may be the key sites of NAA. In conclusion, the NAA-mediated response to Cd stress was closely associated with “defense response” genes in shoots and “oxidoreductase activity, oxidizing metal ions” and “response to auxin” genes in roots.