Carbohydrate metabolism is a determinant for the host specificity of baculovirus infections

Comparative transcriptome analysis reveals disruption of Plutella xylostella immune system by fungal peptide cyclosporin C

The diamondback moth (Plutella xylostella), a major threat to crucifers across the globe, has developed resistance against the majority of insecticides enhancing the need for alternate control measures against this pest. Recently cyclosporin C, a secondary metabolite produced by the insect pathogenic fungus Purpeocillium lilacinum, has been reported to induce lethal and sub-lethal effects against P. xylostella. To date, little is known about the molecular mechanisms of interaction between cyclosporin C and P. xylostella immune systems. This study reports the transcriptome-based immune response of P. xylostella to cyclosprin C treatment. Our results showed differential expression of 322, 97, and 504 differentially expressed genes (DEGS) in P. xylostella treated with cyclosporin C compared to control 24, 48, and 72 h post-treatment, respectively. Thirteen DEGs were commonly expressed at different time intervals in P. xylostella larvae treated with cyclosporin C compared to control. Cyclosporin C treatment induced the down-regulated expression of majority of immune-related genes related to pattern recognition responses, signal modulation, Toll and IMD pathways, antimicrobial peptides and antioxidant responses confirming the ability to suppress immune response of P. xylostella. These results will further improve our knowledge of the infection mechanism and complex biochemical processes involved in interaction between cyclosporin C and insect immune systems.

Virus-host coevolutionary analyses of an Alphabaculovirus with a wide host range

Baculoviruses are highly host specific, and their host range is usually restricted to a single or a few closely related insect species, except for few virus species, e.g. Alphabaculovirus aucalifonicae and Alphabaculovirus mabrassicae. In this study, two new alphabaculovirus isolates were isolated from the larvae of Mamestra brassicae and Mythimna separata, which were named as Mamestra brassicae multiple nucleopolyhedrovirus isolate QD (MbMNPV-QD) and Mythimna separata multiple nucleopolyhedrovirus isolate Hb (MyseMNPV-Hb), respectively. The Kimura two-parameter values based on the concatenated 38 core genes of baculovirus revealed that MbMNPV (isolates QD/CHb1/K1/CTa), MyseMNPV-Hb, Helicoverpa armigera multiple nucleopolyhedrovirus (HearMNPV) and Mamestra configurata nucleopolyhedrovirus B (MacoNPV-B) were different isolates of a same virus species. A phylogenetic tree of baculoviruses and nudiviruses constructed from their 20 homologous gene sequences, and that of their isolated hosts constructed from 13 protein-coding genes of the insect mitochondrial genomes, were used to analyse the coevolution of baculoviruses with their isolated hosts. The results showed that M. brassicae was the most likely ancestral host of these virus isolates, included MbMNPV isolates, MyseMNPV-Hb, HearMNPV, and MacoNPV-B. Therefore, we concluded that these virus isolates belong to the existing virus species - Alphabaculovirus mabrassicae with M. brassicae as their ancestral host.

Rapid production of chimeric silkworm/spider silk with improved mechanical properties by infection of nonpermissive Bombyx mori with recombinant AcMNPV harboring native-size of spidroin genes

Spider silks with excellent mechanical properties attract more attention from scientists worldwide, and the dragline silk that serves as the framework of the spider's web is considered one of the strongest fibers. However, it is unfeasible for large-scale production of spider silk due to its highly territorial, cannibalistic, predatory, and solitary behavior. Herein, to alleviate some of these problems and explore aneasy way to produce spider fibers, we constructed recombinant baculovirus Autographa californica multiple nucleopolyhedrovirus (AcMNPV) simultaneously expressing Trichonephila clavipes native ampullate spidroin 2 (MaSp-G) and spidroin 1 (MaSp-C) driven by the promoters of silkworm fibroin genes, to infect the nonpermissive Bombyx mori larvae at the fifth instar. MaSp-G and MaSp-C were co-expressed in the posterior silk glands (PSGs) of infected silkworms and successfully secreted into the lumen of the silk gland for fibroin globule assembly. The integration of MaSp-G and MaSp-C into silkworm silk fibers significantly improved the mechanical properties of these chimeric silk fibers, especially the strength and extensibility, which may be caused by the increment of β-sheet in the chimeric silkworm/spider silk fiber. These results demonstrated that silkworms could be developed as the nonpermissive heterologous host for the mass production of chimeric silkworm/spider silk fibers via the recombinant baculovirus AcMNPV.

Deacetylation of ACO2 Is Essential for Inhibiting Bombyx mori Nucleopolyhedrovirus Propagation

Bombyx mori nucleopolyhedrovirus (BmNPV) is a specific pathogen of Bombyx mori that can significantly impede agricultural development. Accumulating evidence indicates that the viral proliferation in the host requires an ample supply of energy. However, the correlative reports of baculovirus are deficient, especially on the acetylation modification of tricarboxylic acid cycle (TCA cycle) metabolic enzymes. Our recent quantitative analysis of protein acetylome revealed that mitochondrial aconitase (ACO2) could be modified by (de)acetylation at lysine 56 (K56) during the BmNPV infection; however, the underlying mechanism is yet unknown. In order to understand this regulatory mechanism, the modification site K56 was mutated to arginine (Lys56Arg; K56R) to mimic deacetylated lysine. The results showed that mimic deacetylated mitochondrial ACO2 restricted enzymatic activity. Although the ATP production was enhanced after viral infection, K56 deacetylation of ACO2 suppressed BmN cellular ATP levels and mitochondrial membrane potential by affecting citrate synthase and isocitrate dehydrogenase activities compared with wild-type ACO2. Furthermore, the deacetylation of exogenous ACO2 lowered BmNPV replication and generation of progeny viruses. In summary, our study on ACO2 revealed the potential mechanism underlying WT ACO2 promotes the proliferation of BmNPV and K56 deacetylation of ACO2 eliminates this promotional effect, which might provide novel insights for developing antiviral strategies.

Comparative transcriptome analysis reveals differences in gene expression in whitefly following individual or combined applications of Akanthomyces attenuatus (Zare & Gams) and matrine

BACKGROUND

Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) is a serious pest of crops in different regions of the world. Our recent studies on the joint application of Akanthomyces attenuatus (a pathogenic insect fungus) and matrine (a botanical insecticide) against B. tabaci have shown promising results. Using RNA sequencing (RNA-Seq), we identified differentially expressed genes involved in whitefly responses to single or mixed applications of A. attenuatus and matrine.

METHODS

In this study, we compared the transcriptome profiles of B. tabaci treated with individual and combined treatments of A. attenuatus and matrine to determine variations in gene expression among whiteflies in response to different treatments.

RESULTS

Transcriptomic data analysis showed differential expression of 71, 1194, and 51 genes in response to A. attenuatus (BtA), matrine (BtM), and A. attenuatus + matrine (BtAM) treatment, respectively. A total of 65 common differentially expressed genes (DEGs) were identified between whiteflies treated with A. attenuatus (BtA) and matrine (BtM). A comparison of DEGs across the three treatments (BtA, BtM, and BtAM) revealed two common DEGs. The results also revealed that AMPK signaling, apoptosis, and drug metabolism pathways are likely involved in whitefly defense responses against A. attenuatus and matrine infection. Furthermore, a notable suppression of general metabolism and immune response genes was observed in whiteflies treated with A. attenuatus + matrine (BtAM) compared to whiteflies treated with individual A. attenuatus (BtA) or matrine (BtM) treatments.

CONCLUSION

Dynamic changes in the number of differentially expressed genes were observed in B. tabaci subjected to different treatments (BtA, BtM, and BtAM). To the best of our knowledge, this is the first report on the molecular interactions between whitefly and individual or combined treatments of A. attenuatus and matrine. These results will further improve our knowledge of the infection mechanism and complex biochemical processes involved in the synergistic action of A. attenuatus and matrine against B. tabaci.