The relationship between MHC-peptide interaction and resistance to virus in chickens.

INTRODUCTION: The MHC-peptide interaction has a subtle influence on host resistance to virus. This paper aims to study the relationship between MHC-peptide interaction and MHC-related virus-resistance. METHODS: By 3D homology modeling, the structure of chicken BF2 molecule BF2*0201 (PDB code: 4d0d) was studied and compared with the known structures of BF2 molecule BF2*0401 (PDB code: 4e0r) to elucidate the characteristics of BF2*0201-binding antigenic peptides. RESULTS: The results show that due to the amino acid difference between the two binding groove of 4e0r and 4d0d, the size of the binding groove of the two are 1130 ų and1380 ų respectively, indicating the amino acid species that 4e0r binding peptide has lower selectivity than 4d0d; and because of large side chain conformation of Arg (especially Arg111) of 4e0r replaced by small side chain Tyr111 of 4d0d, the volume of central part of the binding groove of 4d0d is obviously larger than that of 4e0r, indicating that the restrictive of binding antigenic peptides for 4d0d is narrower than that of 4e0r; and on account of the chargeability of the binding groove of the two are different, namely the binding groove chargeability of 4e0r (strong positive polarity) and 4d0d (weak negative polarity). CONCLUSION: There are generally more peptides presented by the BF2 of B2 haplotype than by that of B4 haplotype, leading to more resistance of B2 than that of B4 to virus.

Effect of glycogen synthase and glycogen phosphorylase knockdown on the expression of glycogen- and insulin-related genes in the rice brown planthopper Nilaparvata lugens.

Nilaparvata lugens is a serious threat to rice growth. Glycogen metabolism is one of the important physiological processes of insects, which is mainly regulated by glycogen synthase (GS) and glycogen phosphorylase (GP). In the present study, trehalose content was significantly reduced at 72 h after NlGP and NlGS knockdown, whereas glucose content was significantly increased at both 48 h and 72 h after GS knockdown. RNAi combined with RNA-Seq was used to identify NlGP- and NlGS-related pathways and genes in N. lugens. A total of 593 genes were up-regulated and 5969 genes were down-regulated after NlGP and NlGS knockdown, respectively. Moreover, the NlGS-knockdown group was mapped to 10,967 pathways, whereas the NlGP-knockdown group was mapped to 7948 pathways, and the greatest differences between the groups were associated with carbohydrate, lipid, amino acid and energy metabolism. Meanwhile, 1800, 1217, and 1211 transcripts in the NlGP-knockdown group and 2511, 1666, and 1727 transcripts in the NlGS-knockdown group were involved in bioprocess, cellular ingredients and molecular function, respectively. Almost all these genes were down-regulated by either NlGP or NlGS knockdown, with significant down-regulation of the 6-trehalose phosphate synthase (TPS), trehalase (TRE), GS, GP, phosphoacetylglucosamine mutase (PGM, n = 2), Insulin receptors (InRs) and insulin-like peptides (Ilps) genes. These results have demonstrated that RNAi-mediated NlGP and NlGS knockdown could lead to content of trehalose and glucose out of balance, but have no obvious effect on glycogen content, and have suggested that GS plays more complex role in other metabolism pathway of N. lugens.

Insect Behavior and Physiological Adaptation Mechanisms Under Starvation Stress.

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.

Characterization of the Akirin Gene and Its Role in the NF-κB Signaling Pathway of Sogatella furcifera.

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.