Characterization of neutral lipases revealed the tissue-specific triacylglycerol hydrolytic activity in Nilaparvata lugens

Functional analysis of neutral lipases in bug feeding and reproduction

BACKGROUND

The bean bug, Riptortus pedestris, is known to cause significant economic losses in soybean crops due to its seed-sucking behavior, but the mechanism of its adaptation to lipid-rich seeds remains poorly understood. To exploit potential target genes for controlling this pest, neutral lipases are functionally characterized in this study.

RESULTS

In this study, a total of 69 lipases were identified in R. pedestris, including 35 neutral lipases that underwent significant expansion. The phylogeny, expression patterns, and catalytic capacity of neutral lipases were investigated and we selected six salivary gland-specific, eight gut-specific, and three ovary-specific genes for functional analysis. All three ovary-specific neutral lipases (Chr1.3195, Chr1.0994, and Chr5.0087) are critical for insect reproduction, while a few gut-specific neutral lipases (Chr4.0221 and Chr1.3207) influence insect survivorship or weight gain. In contrast, no significant phenotype change is observed when silencing salivary gland-specific neutral lipases.

CONCLUSION

The lipases Chr1.3195, Chr1.0994, Chr5.0087, Chr4.0221, and Chr1.3207 are essential for R. pedestris feeding and reproduction, and the insect is highly sensitive to their deficiency, suggesting that neutral lipases are promising candidates for application in RNAi-based control of this destructive pest. © 2023 Society of Chemical Industry.

Untargeted Lipidomics Analysis Unravels the Different Metabolites in the Fat Body of Mated Bumblebee (Bombus terrestris) Queens

The fat body has important functions in energy, fertility, and immunity. In female insects, mating stimulates physiological, behavioral, and gene expression changes. However, it remains unclear whether the metabolites in the fat body are affected after the bumblebee (Bombus terrestris) queen mates. Here, the ultrastructure and lipid metabolites in fat body of mated queens were compared with those of virgins. The fat body weight of mated bumblebee queens was significantly increased, and the adipocytes were filled with lipid droplets. Using LC-MS/MS-based untargeted lipidomics, 949 and 748 differential metabolites were identified in the fat body of virgin and mated bumblebee queens, respectively, in positive and negative ion modes. Most lipid metabolites were decreased, especially some biomembrane components. In order to explore the relationship between the structures of lipid droplets and metabolite accumulation, transmission electron microscopy and fluorescence microscopy were used to observe the fat body ultrastructure. The size/area of lipid droplets was larger, and the fusion of lipid droplets was increased in the mated queen's fat body. These enlarged lipid droplets may store more energy and nutrients. The observed differences in lipid metabolites in the fat body of queens contribute to understanding the regulatory network of bumblebees post mating.

Transcriptomic analysis of Mythimna separata ovaries and identification of genes involved in reproduction

The migratory insect Mythimna separata is a major pest of grain crops in Asia. Unfortunately, the molecular mechanisms that control and regulate reproduction in this species remain unclear. In this study, transcriptome sequencing was utilized to identify genes associated with ovary development and oogenesis. Clean sequences totaling 117.71 Gb were assembled into 178,534 unigenes with a mean length of 647.37 bp and N50 length of 837 bp. Transcriptome analysis showed that 7921 unigenes were significantly expressed in ovaries with 4403 and 3518 unigenes up- and down-regulated, respectively. Enrichment analysis with the Kyoto Encyclopedia of Genes and Genomes database suggested that 729 differentially expressed genes were significantly enriched in the top 20 pathways (q-values <0.05). Twenty genes were associated with ovary development and oogenesis and included lipases, Nanos, small heat shock proteins (sHsps) and histones; these were further verified by qRT-PCR and may play essential roles in M. separata reproduction. Collectively, our findings reveal underlying mechanisms of M.separata reproduction and may lead to RNAi-based management strategies targeting reproductive physiology.