RNA-seq analysis of the differential response to low-temperature stress in two morphs of mud crabs (Scylla paramamosain)

Comprehensive analysis of butyric acid impact on immunology, histopathology, gene expression, and metabolomic responses in pacific shrimp experiencing cold stress

In this study, our objective was to investigate the impact of dietary butyric acid (BA) on the homeostasis mechanism of Pacific shrimp under cold stress. Specifically, we analyzed its effects on immunity, antioxidant capacity, gene expression, and metabolomics response. To carry out this research, Litopenaeus vannamei were fed a diet supplemented with BA for 8 weeks. Following this feeding period, a total of 180 shrimp, with an average weight of 12.76 ± 0.38 g, were exposed to cold conditions, with the temperature decreasing from 28 °C to 14 °C within an hour. The results of our study revealed survival rates ranging from 90 % to 100 %. Shrimp that were fed a diet containing 1.5 % BA exhibited a significant increase in acid phosphatase (ACP) and alkaline phosphatase (AKP) activity. Conversely, the control groups showed an increase in aspartate aminotransferase (AST) and alanine transaminase (ALT) activity. Shrimp that consumed diets containing 1.5 % BA displayed the lowest malondialdehyde (MDA) levels with the highest superoxide dismutase (SOD) content. The shrimp fed the BA diet exhibited tightly organized hepatic tubules with a star-shaped lumen filled with numerous B and R cells. Furthermore, shrimp fed the BA diet demonstrated a significant increase in caspase 3 (CASP) expression. There were no significant variations in the expression levels of prophenoloxidase (ProPO), manganese superoxide dismutase (MnSOD), and glutathione S-transferase (GST) The metabolites of Dl-carnitine, acetyl-l-carnitine, propionylcarnitine, hexanoylcarnitine, palmitoylcarnitine, decanoylcarnitine, and Dl-carnitine exhibited significantly increased expression in shrimp that were fed BA, suggesting their role in the lipolysis process. Based on the findings, adding 2 % BA to the diet of Pacific shrimp helps reduce inflammation and oxidative stress when they are under cold stress.

Integrated physiological, transcriptome, and metabolome analyses of the hepatopancreas of Litopenaeus vannamei under cold stress

Temperature is a limiting factor in the growth of aquatic organisms and can directly affect many chemical and biological processes, including metabolic enzyme activity, aerobic respiration, and signal transduction. In this study, physiological, transcriptomic, and metabolomic analyses were performed to characterize the response of Litopenaeus vannamei to cold stress. We subjected L. vannamei to gradually decreasing temperatures (24 °C, 20 °C, 18 °C, 14 °C, and 12 °C) and studied the changes in the hepatopancreas. The results showed that extreme cold stress (12 °C) caused structural damage to the hepatopancreas of L. vannamei. However, shrimp exhibited response mechanisms to enhance cold tolerance, through regulating changes in key genes and metabolites in amino acid, lipid metabolism, and carbohydrate metabolism, including (a) increased level of methylation in cells to enhance cold tolerance; (b) increased content of critical amino acids, such as proline, alanine, glutamic acid and taurine, to ameliorate energy metabolism, protect cells from cold-induced osmotic imbalance, and promote ion transport and DNA repair; (c) accumulation of unsaturated fatty acids to improve cell membrane fluidity; and (d) regulation of the metabolic pattern shift to rely on anaerobic metabolism with a gradual decrease in aerobic metabolism and enhance glycolysis to produce enough ATP to maintain energy metabolic balance. When the temperature dropped further, cold stress impaired antioxidant and immune defense responses in shrimp. This study provides an integrated analysis of the physiology, transcriptome, and metabolome of L. vannamei in response to cold stress.

De novo genome assembly of the invasive mosquito species Aedes japonicus and Aedes koreicus

BACKGROUND

Recently, two invasive Aedes mosquito species, Ae. japonicus and Ae. koreicus, are circulating in several European countries posing potential health risks to humans and animals. Vector control is the main option to prevent mosquito-borne diseases, and an accurate genome sequence of these mosquitoes is essential to better understand their biology and to develop effective control strategies.

METHODS

A de novo genome assembly of Ae. japonicus (Ajap1) and Ae. koreicus (Akor1) has been produced based on a hybrid approach that combines Oxford Nanopore long-read and Illumina short-read data. Their quality was ascertained using various metrics. Masking of repetitive elements, gene prediction and functional annotation was performed.

RESULTS

Sequence analysis revealed a very high presence of repetitive DNA and, among others, thermal adaptation genes and insecticide-resistance genes. Through the RNA-seq analysis of larvae and adults of Ae. koreicus and Ae. japonicus exposed to different temperatures, we also identified genes showing a differential temperature-dependent activation.

CONCLUSIONS

The assembly of Akor1 and Ajap1 genomes constitutes the first updated collective knowledge of the genomes of both mosquito species, providing the possibility of understanding key mechanisms of their biology such as the ability to adapt to harsh climates and to develop insecticide-resistance mechanisms.