Annotation of glycolysis, gluconeogenesis, and trehaloneogenesis pathways provide insight into carbohydrate metabolism in the Asian citrus psyllid

Glucose transporter 2‑transported glucosamine inhibits glycolysis in cancer cell lines through competition with glucose for hexokinase II

Antiproliferative effects of glucosamine, a glucose derivative with a similar structure to glucose, have been discovered, but the molecular mechanisms are not yet fully understood. Since glucosamine and glucose not only have similar structures but also are catalyzed by the same enzyme, hexokinase (HK), the present study delved into determining whether the antiproliferative effect of glucosamine involved the inhibition of glycolysis by competition with glucose. Whole‑genome screening analysis showed that a number of the gene pathways controlled by glucosamine were directly and indirectly involved in glycolysis. In vitro experiments revealed that as more glucose was added, the antiproliferative effect of glucosamine decreased. Also, it was found that glucosamine was transported into cells mainly through glucose transporter (GLUT) 2 which was responsible for the antiproliferative effects of glucosamine. In addition, the present study found that cancer cell lines with low expression level of HKII show high sensitivity to glucosamine and a HK inhibitor, 3‑bromopyruvate, enhanced the antiproliferative effect of glucosamine. Under hypoxic conditions, activated hypoxia‑inducible factor 1α (HIF‑1α) inducing glucose uptake and glycolysis hampered glucosamine‑induced cell death and HIF1A knockdown or HK inhibitors restored the antiproliferative effects of glucosamine. These findings demonstrated that glucosamine is an efficient glycolysis inhibitor and that GLUT2 and HKII play important roles as biomarkers for determining sensitivity to glucosamine. Moreover, the results suggested that the antiproliferative effect of glucosamine may be more efficient when administered in combination with other glycolytic agents or inhibitors targeting HIF‑1α.

Understanding the role of trehalose in interactions between Wolbachia and Aedes aegypti

Mosquito-borne diseases such as chikungunya, dengue, and Zika represent a major burden on global public health. To fight against these arboviruses, vector control strategies are a priority. One existing strategy is based on the use of an endosymbiotic bacterium, Wolbachia, which reduces the transmission of arboviruses by the mosquito Aedes aegypti via a pathogen blocking effect. Wolbachia in Ae. aegypti disrupts several pathways of the host's metabolism. Trehalose is a carbohydrate circulating mainly in insect hemolymph and plays a role in numerous mechanisms as energy source or stress recovery molecule and in chitin synthesis. This study explores the importance of trehalose in the interactions between Wolbachia and Ae. aegypti, and attempts to understand the pathogen blocking effect.

Diaci v3.0: chromosome-level assembly, de novo transcriptome, and manual annotation of Diaphorina citri, insect vector of Huanglongbing

BACKGROUND

Diaphorina citri is an insect vector of "Candidatus Liberibacter asiaticus" (CLas), the gram-negative bacterial pathogen associated with citrus greening disease. Control measures rely on pesticides with negative impacts on the environment, natural ecosystems, and human and animal health. In contrast, gene-targeting methods have the potential to specifically target the vector species and/or reduce pathogen transmission.

RESULTS

To improve the genomic resources needed for targeted pest control, we assembled a D. citri genome based on PacBio long reads followed by proximity ligation-based scaffolding. The 474-Mb genome has 13 chromosomal-length scaffolds. In total, 1,036 genes were manually curated as part of a community annotation project, composed primarily of undergraduate students. We also computationally identified a total of 1,015 putative transcription factors (TFs) and were able to infer motifs for 337 TFs (33%). In addition, we produced a genome-independent transcriptome and genomes for D. citri endosymbionts.

CONCLUSIONS

Manual annotation provided more accurate gene models for use by researchers and provided an excellent training opportunity for students from multiple institutions. All resources are available on CitrusGreening.org and NCBI. The chromosomal-length D. citri genome assembly serves as a blueprint for the development of collaborative genomics projects for other medically and agriculturally significant insect vectors.

Host plant-induced changes in metabolism and osmotic regulation gene expression in Diaphorina citri adults

The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Liviidae), is a worldwide citrus pest. It transmits the pathogen Candidatus Liberibacter spp. of Huanglongbing (HLB), causing severe economic losses to the citrus industry. Severalgenera of plants in the Rutaceae family are the hosts of D. citri. However, the impact of these hosts on the metabolism and osmotic regulation gene expression of the pest remains unexplored. In this study, the contents of total sugars, sucrose, fructose, and glucose in young shoots, old leaves, and young leaves of 'Shatangju' mandarin and Murraya exotica were analyzed. Metabolomic analysis found that sucrose and trehalose were more abundant in the gut samples of D. citri adults fed on M. exotica when compared to what's in 'Shatangju' mandarin. A total of six aquaporin genes were identified in D. citri through the genome and transcriptome data. Subsequently, the expression patterns of these genes were investigated with respect to their developmental stage and tissue specificity. Additionally, the expression levels of osmotic regulation and trehalose metabolism genes in adults fed on different plants were evaluated. Our results provide useful information on the transfer of sugar between plants and D. citri. Our results preliminary revealed the sugar metabolism regulation mechanism in D. citri adults.

PEPCK and glucose metabolism homeostasis in arthropods

The fat body is responsible for a variety of functions related to energy metabolism in arthropods, by controlling the processes of de novo glucose production (gluconeogenesis) and glycogen metabolism. The rate-limiting factor of gluconeogenesis is the enzyme phosphoenolpyruvate carboxykinase (PEPCK), generally considered to be the first committed step in this pathway. Although the study of PEPCK and gluconeogenesis has been for decades restricted to mammalian models, especially focusing on muscle and liver tissue, current research has demonstrated particularities about the regulation of this enzyme in arthropods, and described new functions. This review will focus on arthropod PEPCK, discuss different aspects to PEPCK regulation and function, its general role in the regulation of gluconeogenesis and other pathways. The text also presents our views on potentially important new directions for research involving this enzyme in a variety of metabolic adaptations (e.g. diapause), discussing enzyme isoforms, roles during arthropod embryogenesis, as well as involvement in vector-pathogen interactions, contributing to a better understanding of insect vectors of diseases and their control.