Protein–DNA interactions in the promoter region of the gene encoding diapause hormone and pheromone biosynthesis activating neuropeptide of the cotton bollworm, Helicoverpa armigera

CBR1 decreases protein carbonyl levels via the ROS/Akt/CREB pathway to extend lifespan in the cotton bollworm, Helicoverpa armigera

Reactive oxygen species (ROS) are considered a major cause of ageing and ageing-related diseases through protein carbonylation. Little is known about the molecular mechanisms that confer protection against ROS. Here, we observed that, compared with nondiapause-destined pupae, high protein carbonyl levels are present in the brains of diapause-destined pupae, which is a 'non-ageing' phase in the moth Helicoverpa armigera. Protein carbonyl levels respond to ROS and decrease metabolic activity to induce diapause in order to extend lifespan. However, protein carbonylation in the brains of diapause-destined pupae still occurs at a physiological level compared to young adult brains. We find that ROS activate Akt, and Akt then phosphorylates the transcription factor CREB to facilitate its nuclear import. CREB binds to the promoter of carbonyl reductase 1 (CBR1) and regulates its expression. High CBR1 levels reduce protein carbonyl levels to maintain physiological levels. This is the first report showing that the moth brain can naturally control protein carbonyl levels through a distinct ROS-Akt-CREB-CBR1 pathway to extend lifespan.

COXIV and SIRT2-mediated G6PD deacetylation modulate ROS homeostasis to extend pupal lifespan

Previous studies have shown that high physiological levels of reactive oxygen species (ROS) in the brain promote pupal diapause, which extends the pupal lifespan. However, the molecular mechanisms of ROS generation are unclear. In this paper, we found that mitochondrial ROS (mtROS) levels in the brains of Helicoverpa armigera diapause-destined pupae (DP) were higher and that the expression of cytochrome oxidase subunit IV (COXIV) was lower than in NP. In addition, downregulating COXIV caused mitochondrial dysfunction which elevated mtROS levels. Protein kinase A (PKA) was downregulated in DP, which led to the downregulated expression of the mitochondrial transcription factor TFAM. Low TFAM activity failed to promote COXIV expression and resulted in the high ROS levels that induced diapause. In addition, low sirtuin 2 expression suppressed glucose-6-phosphate dehydrogenase (G6PD) deacetylation at K382, which led to reduced G6PD activity and low NADPH levels, thereby maintaining high levels of ROS. Two proteins, COXIV and G6PD, thus play key roles in the elevated accumulation of ROS that induce diapause and extend the pupal lifespan.

Insect Transcription Factors: A Landscape of Their Structures and Biological Functions in Drosophila and beyond

Transcription factors (TFs) play essential roles in the transcriptional regulation of functional genes, and are involved in diverse physiological processes in living organisms. The fruit fly Drosophila melanogaster, a simple and easily manipulated organismal model, has been extensively applied to study the biological functions of TFs and their related transcriptional regulation mechanisms. It is noteworthy that with the development of genetic tools such as CRISPR/Cas9 and the next-generation genome sequencing techniques in recent years, identification and dissection the complex genetic regulatory networks of TFs have also made great progress in other insects beyond Drosophila. However, unfortunately, there is no comprehensive review that systematically summarizes the structures and biological functions of TFs in both model and non-model insects. Here, we spend extensive effort in collecting vast related studies, and attempt to provide an impartial overview of the progress of the structure and biological functions of current documented TFs in insects, as well as the classical and emerging research methods for studying their regulatory functions. Consequently, considering the importance of versatile TFs in orchestrating diverse insect physiological processes, this review will assist a growing number of entomologists to interrogate this understudied field, and to propel the progress of their contributions to pest control and even human health.

Hexokinase is a key regulator of energy metabolism and ROS activity in insect lifespan extension

Developmental arrest (diapause) is a ‘non-aging’ state that is similar to the Caenorhabditis elegans dauer stage and Drosophila lifespan extension. Diapause results in low metabolic activity and a profound extension of insect lifespan. Here, we cloned the Helicoverpa armigera Hexokinase (HK) gene, a gene that is critical for the developmental arrest of this species. HK expression and activity levels were significantly increased in nondiapause-destined pupae compared with those of diapause-destined pupae. Downregulation of HK activity reduced cell viability and delayed pupal development by reducing metabolic activity and increasing ROS activity, which suggests that HK is a key regulator of insect development. We then identified the transcription factors Har-CREB, -c-Myc, and -POU as specifically binding the Har-HK promoter and regulating its activity. Intriguingly, Har-POU and -c-Myc are specific transcription factors for HK expression, whereas Har-CREB is nonspecific. Furthermore, Har-POU and -c-Myc could respond to ecdysone, which is an upstream hormone. Therefore, low ecdysone levels in diapause-destined individuals lead to low Har-POU and -c-Myc expression levels, ultimately repressing Har-HK expression and inducing entry into diapause or lifespan extension.

Fork head transcription factor is required for ovarian mature in the brown planthopper, Nilaparvata lugens (Stål)

Background

The brown planthopper (BPH), Nilaparvata lugens, is the most devastating rice pest in many areas throughout Asia. The reproductive system of female N. lugens consists of a pair of ovaries with 24-33 ovarioles per ovary in most individuals which determine its fecundity. The fork head (Fox) is a transcriptional regulatory molecule, which regulates and controls many physiological processes in eukaryotes. The Fox family has several subclasses and members, and several Fox factors have been reported to be involved in regulating fecundity.

Results

We have cloned a fork head gene in N. lugens. The full-length cDNA of NlFoxA is 1789 bp and has an open reading frame of 1143 bp, encoding a protein of 380 amino acids. Quantitative real-time PCR (RT-qPCR) and Reverse Transcription- PCR (RT-PCR) analysis revealed that NlFoxA mRNA was mainly expressed in the fat body, midgut, cuticle and Malpighian tube, and was expressed continuously with little change during all the developmental stages. NlFoxA belongs to the FoxA subfamily of the Fox transcription factors. Knockdown of NlFoxA expression by RNAi using artificial diet containing double-stranded RNA (dsRNA) significantly decreased the number of offspring and impacted the development of ovaries. ELISA and Western blot analyses showed that feeding-based RNAi of NlFoxA gene also resulted in decreased expression of vitellogenin (Vg) protein.

Conclusion

NlFoxA plays an important role in regulation of fecundity and development of ovaries in the BPH via regulating vitellogenin expression.

Transcription factor fork head regulates the promoter of diapause hormone gene in the cotton bollworm, Helicoverpa armigera, and the modification of SUMOylation

The transcription factor fork head (FoxA) plays important roles in development and metabolism. Here, we cloned a fork head gene in Helicoverpa armigera, and found that the fork head protein is mainly located in the nucleus. This fork head gene belongs to the FoxA subfamily of the Fox transcription factors. The diapause hormone and pheromone biosynthesis-activating neuropeptide (DH-PBAN), which are two well-documented insect neuropeptides that regulate insect development and pheromone biosynthesis, are encoded by a single mRNA. In the present study, fork head was shown to bind strongly to the promoter of H. armigera DH-PBAN gene, and regulate its promoter activity. Furthermore, the effect of SUMOylation of the FH protein on the regulation of Har-DH-PBAN gene was investigated, and we show that the SUMO can modify Har-FH protein and cause down-regulation of DH-PBAN gene expression. These results suggest that SUMOylated FH plays a key role in insect diapause in H. armigera.

Transcriptional regulation of the gene for prothoracicotropic hormone in the silkworm, Bombyx mori

Prothoracicotropic hormone (PTTH) is one of key players in regulation of insect growth, molting, metamorphosis, diapause, and is expressed specifically in the two pairs of lateral PTTH-producing neurosecretory cells in the brain. Analysis of cis-regulatory elements of the PTTH promoter might elucidate the regulatory mechanism controlling PTTH expression. In this study, the PTTH gene promoter of Bombyx mori (Bom-PTTH) was cloned and sequenced. The cis-regulatory elements in Bom-PTTH gene promoter were predicted using Matinspector software, including myocyte-specific enhancer factor 2, pre-B-cell leukemia homeobox 1, TATA box, etc. Transient transfection assays using a series of fragments linked to the luciferase reporter gene indicated that the fragment spanning -110 to +33 bp of the Bom-PTTH promoter showed high ability to support reporter gene expression, but the region of +34 to +192 bp and -512 to -111 bp repressed the promoter activity in the BmN and Bm5 cell lines. Electrophoretic mobility shift assays demonstrated that the nuclear protein could specifically bind to the region spanning -124 to -6 bp of the Bom-PTTH promoter. Furthermore, we observed that the nuclear protein could specifically bind to the -59 to -30 bp region of the Bom-PTTH promoter. A classical TATA box, TATATAA, localized at positions -47 to -41 bp, which is a potential site for interaction with TATA box binding protein (TBP). Mutation of this TATA box resulted in no distinct binding band. Taken together, TATA box was involved in regulation of PTTH gene expression in B. mori.

Identification of an E-box DNA binding protein, activated protein 4, and its function in regulating the expression of the gene encoding diapause hormone and pheromone biosynthesis-activating neuropeptide in Helicoverpa armigera

Activated protein 4 (AP-4), an E-box DNA-binding protein, was cloned from the cotton bollworm, Helicoverpa armigera (Har). The expression of Har-AP-4 mRNA and the protein that it encodes are significantly higher in nondiapause pupae than in diapause pupae. In vitro-translated Har-AP-4 can bind specifically to the E-box motif on the promoter of the diapause hormone and pheromone biosynthesis-activating neuropeptide (DH-PBAN). Har-AP-4, fused with the green fluorescent protein (GFP), is localized to the nucleus, and overexpression of Har-AP-4 can significantly activate the promoter of the DH-PBAN gene that is involved in nondiapause pupal development in H. armigera. These results suggest that Har-AP-4, which binds to the promoter of DH-PBAN, may play a role in regulating pupal development in H. armigera.

Developmentally regulated synthesis of p8, a stress-associated transcription cofactor, in diapause-destined embryos of Artemia franciscana

Diapause-destined embryos of the crustacean Artemia franciscana arrest as gastrulae, acquire extreme stress tolerance, and enter profound metabolic dormancy. Among genes upregulated at 2 days postfertilization in these embryos is a homologue of p8, a stress-inducible transcription cofactor. Artemia p8 is smaller than vertebrate homologues but shares a basic helix-loop-helix domain and a bipartite nuclear localization signal. Probing of restriction digested DNA on Southern blots indicated a single Artemia p8 gene and 5'-RACE specified 2 transcription start sites. Several putative cis-acting regulatory sequences, including two heat shock elements, appeared upstream of the p8 transcription start site. Artemia p8 mRNA increased sharply at 1 day postfertilization in diapause-destined embryos and then declined, whereas p8 protein appeared 2 days postfertilization and remained relatively constant throughout development, indicating a stable protein. p8 was not detectable in nauplius-destined (nondiapause) Artemia embryos. Immunofluorescent staining revealed p8 within Artemia nuclei. The results support the idea that p8, a known stressresponsive transcription cofactor, mediates gene expression in diapause-destined Artemia embryos. p8 is the first diapause-related transcription factor identified in crustaceans and 1 of only a small number of such proteins identified in any organism undergoing diapause.