The prothoracic gland (PG) is an important endocrine organ of synthesis and secretion of ecdysteroids that play critical roles in insects. Here, we used a comparative transcriptomic approach to characterize some common features of PGs from two lepidopteran speciesBombyx moriandAntheraea pernyi. Functional and pathway annotations revealed an overall similarity in gene profile between the two PG transcriptomes. As expected, almost all steroid hormone biosynthesis genes and the prothoracicitropic hormone receptor gene (Torso) were well represented in the two PGs. Impressively, two ecdysone receptor genes, eleven juvenile hormone related genes, more than 10 chemosensory protein genes, and a set of genes involved in circadian clock were also presented in the two PGs. Quantitative real time -PCR (qRT-PCR) validated the expression of 8 juvenile hormone and 12 clock related genes inB. moriPG, and revealed a different expression pattern during development in whole fifth larval instar. This contribution to insect PG transcriptome data will extend our understanding of the function and regulation of this important organ.

The Antheraea pernyi nucleopolyhedrovirus (ApNPV) is an exclusive pathogen of A. pernyi. The intense interactions between ApNPV and A. pernyi cause a series of physiological and pathological changes to A. pernyi. However, no detailed report exists regarding the molecular mechanisms underlying the interactions between ApNPV and A. pernyi. In this study, four cDNA libraries of the A. pernyi midgut, including two ApNPV-infected groups and two control groups, were constructed for transcriptomic analysis to provide new clues regarding the molecular mechanisms that underlie these interactions. The transcriptome of the A. pernyi midgut was de novo assembled using the Trinity platform because of the lack of a genome resource for A. pernyi. Compared with the controls, a total of 5,172 differentially expressed genes (DEGs) were identified, including 2,183 up-regulated and 2,989 down-regulated candidates, of which 2,965 and 911 DEGs were classified into different GO categories and KEGG pathways, respectively. The DEGs involved in A. pernyi innate immunity were classified into several categories, including heat-shock proteins, apoptosis-related proteins, serpins, serine proteases and cytochrome P450s. Our results suggested that these genes were related to the immune response of the A. pernyi midgut to ApNPV infection via their essential roles in regulating a variety of physiological processes. Our results may serve as a basis for future research not only on the molecular mechanisms of ApNPV invasion but also on the anti-ApNPV mechanism of A. pernyi.

Antheraea pernyi Guérin-Méneville is used for silk production and as a food resource. Its infection by exogenous pathogens, including microsporidia, fungi, bacteria, and virus, can lead to silkworm diseases, causing major economic losses. A trypsin-like serine protease gene (TLS) was found in A. pernyi transcriptome data resulting from two different infection experiments. The cDNA sequence of ApTLS was 1,020 bp in length and contained an open reading frame of 774 bp encoding a 257-amino acid protein (GenBank KF779933). The present study investigated the expression patterns of ApTLS after exposure to different pathogens, and in four different A. pernyi strains. Semiquantitative RT-PCR indicated that ApTLS was expressed in all developmental stages and was most expressed in the midgut. Quantitative real-time PCR indicated ApTLS was upregulated in the midgut of A. pernyi exposed to nucleopolyhedrovirus (ApNPV), Nosema pernyi, Enterococcus pernyi, and Beauveria bassiana infections, and the highest gene expression level was found under ApNPV infection. The strain Shenhuang No. 2 presented the lowest infection rate and the highest ApTLS gene expression level when exposed to ApNPV. Thus, ApTLS seems to be involved in innate defense reactions in A. pernyi.