Biology subjects

Adams, V. E.

Publications and source records attributed to Adams, V. E..

3 recordsLinked to original sources

bioRxiv2025

Tissue- and temperature-dependent expression, enzyme activity, and RNAi knockdown of Catalase in a freeze-tolerant insect

Organisms that overwinter in temperate climates may experience freezing and freezing-induced oxidative stress during winter. While many insect species can survive freezing, molecular tools such as RNA interference (RNAi) or CRISPR have not been used to understand the physiological mechanisms underlying freeze tolerance. The spring field cricket Gryllus veletis can survive freezing following a 6-week fall-like acclimation. We used RNAi of an antioxidant enzyme in G. veletis to test the hypothesis that minimizing oxidative stress is important for freeze tolerance. In fat body tissue, Catalase mRNA abundance and enzyme activity increased during the acclimation that induces freeze tolerance. Other tissues such as midgut and Malpighian tubules had more stable or lower Catalase expression and activity during acclimation. In unacclimated (freeze-intolerant) crickets, RNA interference (RNAi) effectively knocked down production of the Catalase mRNA and protein in fat body and midgut, but not Malpighian tubules. In acclimated (freeze-tolerant) crickets, RNAi efficacy was temperature-dependent, functioning well at warm (c. 22{degrees}C) but not cool (15{degrees}C or lower) temperatures. This highlights a challenge of using RNAi in cold-acclimated organisms, as they may need to be warmed up for RNAi to work, potentially affecting their stress physiology. Knockdown of Catalase via RNAi in acclimated crickets also had no effect on the ability of the crickets to survive a mild freeze treatment, suggesting that Catalase may not be necessary for freeze tolerance. Our study is the first to demonstrate that RNAi is possible in a freeze-tolerant insect, but further research is needed to examine whether other genes and antioxidant molecules are important in freeze tolerance of G. veletis. HighlightsO_LICatalase expression and activity are elevated in freeze-tolerant cricket fat body C_LIO_LIRNAi knocks down Catalase in fat body and midgut at a warm temperature (22{degrees}C) C_LIO_LIRNAi is not effective at a cool temperature (15{degrees}C) that preserves freeze tolerance C_LIO_LICatalase knockdown has no impact on survival of a mild freeze treatment C_LIO_LIThe role of antioxidants in freeze tolerance warrants further study C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=77 SRC="FIGDIR/small/637938v1_ufig1.gif" ALT="Figure 1"> View larger version (20K): org.highwire.dtl.DTLVardef@1c4d9b8org.highwire.dtl.DTLVardef@b1c304org.highwire.dtl.DTLVardef@7a421eorg.highwire.dtl.DTLVardef@8af62f_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗

bioRxiv2024

HSP70 is upregulated after heat but not freezing stress in the freeze-tolerant cricket Gryllus veletis

Heat shock proteins (HSPs) are well known to prevent and repair protein damage caused by various abiotic stressors, but their role in low temperature and freezing stress is not well-characterized compared to other thermal challenges. Ice formation in and around cells is hypothesized to cause protein damage, yet many species of insects can survive freezing, suggesting HSPs may be an important mechanism in freeze tolerance. Here, we studied HSP70 in a freeze-tolerant cricket Gryllus veletis to better understand the role of HSPs in this phenomenon. We measured expression of one heat-inducible HSP70 isoform at the mRNA level (using RT-qPCR), as well as the relative abundance of total HSP70 protein (using semi-quantitative Western blotting), in five tissues from crickets exposed to a survivable heat treatment (2 h at 40{degrees}C), a 6-week fall-like acclimation that induces freeze tolerance, and a survivable freezing treatment (1.5 h at -8{degrees}C). While HSP70 expression was upregulated by heat at the mRNA or protein level in all tissues studied (fat body, Malphigian tubules, midgut, femur muscle, nervous system ganglia), no tissue exhibited HSP70 upregulation within 2 - 24 h following a survivable freezing stress. During fall-like acclimation to mild low temperatures, we only saw moderate upregulation of HSP70 at the protein level in muscle, and at the RNA level in fat body and nervous tissue. Although HSP70 is important for responding to a wide range of stressors, our work suggests that this chaperone may be less critical in the preparation for, and response to, moderate freezing stress. HighlightsO_LIHeat shock protein 70 (HSP70) may not contribute substantially to freeze tolerance C_LIO_LIHeat stress caused HSP70 mRNA and protein upregulation in the spring field cricket C_LIO_LIAcclimation prior to freezing was correlated with slight HSP70 upregulation C_LIO_LIHSP70 was not upregulated after freezing in this freeze-tolerant insect C_LIO_LIFurther work is needed to determine whether freezing causes protein damage C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=72 SRC="FIGDIR/small/621172v1_ufig1.gif" ALT="Figure 1"> View larger version (18K): org.highwire.dtl.DTLVardef@170fda7org.highwire.dtl.DTLVardef@11cf432org.highwire.dtl.DTLVardef@1e41be9org.highwire.dtl.DTLVardef@e46c4d_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗

bioRxiv2024

Invasive adult jumping worms in Atlantic Canada are chill-susceptible

The jumping worm Amynthas tokioensis is invasive in North America, and it has been expanding its range northward in recent years. Because low temperatures typically restrict the geographic distribution of organisms, our goal was to characterize the cold tolerance physiology of adult jumping worms from a site in New Brunswick, Canada (c. 45{degrees}N), with the intent of better understanding their geographic range limits. Most of our experiments supported the conclusion that these worms are chill-susceptible: they die during or after exposure to relatively mild low temperatures. When gradually cooled, adult worms lost neuromuscular coordination at approximately 0 {degrees}C and froze at a mean temperature of -4.5 {degrees}C. They did not survive freezing and showed poor survival following 1 h exposures to 0 {degrees}C and subzero temperatures. At higher mild temperatures (5 {degrees}C), the worms could survive short (up to 6 h) but not long (e.g., 48 h) chilling durations. We attempted to induce improved cold tolerance via a five-week gradual acclimation to fall-like temperatures, but fall-acclimated worms showed poor survival during and after this acclimation. Acclimation also did not induce accumulation of glucose, a typical cryoprotectant in earthworms. We suggest that A. tokioensis can likely persist wherever the growing season is sufficiently warm and long enough for the adults to mature, reproduce, and lay cocoons prior to the chilling temperatures associated with early fall. Future work examining the cold tolerance of the overwintering cocoons will be important for fully understanding the northern range limits of these jumping worms.

zoology↗