Knockdown of heat shock transcription factor 1 decreases temperature stress tolerance in Bemisia tabaci MED

Heat-shock protein 70 reduces apoptosis in the gills and hepatopancreas of Marsupenaeus japonicus under low-temperature stress

The heat shock response (HSR) has important functions in a cell's reaction to stresses. The HSR is regulated and effected by heat shock proteins (HSPs) and heat shock factors (HSFs). Herein, the full-length cDNA of Marsupenaeus japonicus heat shock protein 70 (MjHSP70) was isolated and sequenced. The MjHSP70 cDNA comprised 2346 bp with an open reading frame of 1959 bp, encoding a protein of 653 amino acids. Both MjHSF1 and MjHSP70 are widely expressed across tissues. In response to low temperature stress, MjHSF1 and MjHSP70 expression levels were significantly upregulated in the gill and hepatopancreas. After RNA interference-mediated knockdown of MjHSP70, the mortality rate of M. japonicus increased significantly under low temperature stress, apoptotic genes, e.g., Mjcaspase3 and Mjbcl2, showed significantly upregulated expression, and the apoptotic cell count also increased. Additionally, dual luciferase assays showed that MjHSF1 activated MjHSP70 transcription, and MjHSP70 expression was downregulated after MjHSF1 silencing. The results of glutathione-S-transferase GST pull-down assays indicated that MjHSP70 interacted with MjHSF1's DNA binding domain. Our findings suggested that the MjHSF1-MjHSP70 axis exerts a vital function in M. japonicus' immune response to cold stress.

Silencing of catalase reduces unfavorable low-temperature tolerance capacity in whiteflies

BACKGROUND

Temperature is a primary factor that determines the eco-geographical distribution and population development of invasive insects. Temperature stress leads to various negative effects, including excess reactive oxygen species (ROS), and catalase (CAT) is a key enzyme against ROS in the antioxidant pathway. The whitefly Bemisia tabaci MED is a typical invasive pest that causes damage worldwide. Our previous studies have shown that CAT promotes whitefly adaptation to high temperature by eliminating ROS. However, the mechanism underlying the low-temperature adaptation of whiteflies is still unknown.

RESULTS

In this study, we investigated the role of CAT in the low-temperature tolerance of B. tabaci MED by analyzing its survival rate, reproduction, and ROS levels at 25 °C (as a control, suitable temperature), 20 °C (moderately decreased temperature), and 4 °C (severely decreased temperature). Silencing of BtCAT1, BtCAT2, or BtCAT3 reduced the viability of whiteflies under a short-term severely decreased temperature (4 °C), which manifested as decreases in survival and fecundity accompanied by significant increases in ROS levels. Moreover, even at a moderately decreased temperature (20 °C), silencing of BtCAT1 led to high ROS levels and low survival rates in adults.

CONCLUSION

Silencing of BtCATs significantly increased the sensitivity of B. tabaci MED to low temperatures. BtCAT1 is likely more essential than other BtCATs for low-temperature tolerance in whiteflies. © 2024 Society of Chemical Industry.

Molecular and functional characterization of heat-shock protein 70 in Aphis gossypii under thermal and xenobiotic stresses

Aphis gossypii, a globally distributed and economically significant pest of several crops, is known to infest a wide range of host plants. Heat shock proteins (Hsps), acting as molecular chaperones, are essential for the insect's environmental stress responses. The present study investigated the molecular characteristics and expression patterns of AgHsp70, a heat shock protein gene, in Aphis gossypii. Our phylogenetic analysis revealed that AgHsp70 shared high similarity with homologs from other insects, suggesting a conserved function across species. The developmental expression profiles of AgHsp70 in A. gossypii showed that the highest transcript levels were observed in the fourth instar nymphs, while the lowest levels were detected in the third instar nymphs. Heat stress and exposure to four different xenobiotics (2-tridecanone, tannic acid, gossypol, and flupyradifurone (4-[(2,2-difluoroethyl)amino]-2(5H)-furanone)) significantly up-regulated AgHsp70 expression. Knockdown of AgHsp70 using RNAi obviously increased the susceptibility of cotton aphids to 2-tridecanone, gossypol and flupyradifurone. Dual-luciferase reporter assays revealed that gossypol and flupyradifurone significantly enhanced the promoter activity of AgHsp70 at a concentration of 10 mg/L. Furthermore, we identified the transcription factor heat shock factor (HSF) as a regulator of AgHsp70, as silencing AgHSF reduced AgHsp70 expression. Our results shed light on the role of AgHsp70 in xenobiotic adaptation and thermo-tolerance.