Fraser, S. D. | bioRxiv Science

bioRxiv2026

Freeze tolerance of a beneficial lady beetle, Hippodamia convergens

The convergent lady beetle Hippodamia convergens is widespread in the Americas and considered an important beneficial insect due to its use in pest control. Early work on this species characterized the beetles as freeze-avoidant (freeze-intolerant), suggesting they survive low winter temperatures by physiologically preventing ice formation to temperatures as low as -15{degrees}C. Here, we show that H. convergens can be freeze-tolerant if ice formation occurs at relatively high temperatures. There was 100% survival following inoculative freezing at -0.5{degrees}C and exposure to -3{degrees}C for 20 hours, as well as freezing that spontaneously occurred in fed beetles exposed to -4{degrees}C for 4 hours. Males exposed to 0{degrees}C or -4{degrees}C for 4 hours had similar mating behaviours (latency to first mating, copulation duration) as control beetles exposed to 4{degrees}C, although sample sizes were too small to determine whether freezing itself had an effect on these behaviours. Several putative cryoprotectants were detected in fat body tissue of H. convergens: glycerol, proline, trehalose, and myo-inositol - in order of abundance. Exposure to -3{degrees}C for 20 hours, whether frozen or unfrozen, did not statistically affect cryoprotectant accumulation, although there was a trend towards increased glycerol following freezing. This study is the first to describe inoculative freeze tolerance in a lady beetle and establishes a baseline for future studies that examine the mechanisms underlying this freeze tolerance and the effects of freezing on reproductive behaviour. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=69 SRC="FIGDIR/small/744689v1_ufig1.gif" ALT="Figure 1"> View larger version (16K): org.highwire.dtl.DTLVardef@1c0382org.highwire.dtl.DTLVardef@12a5932org.highwire.dtl.DTLVardef@145f4adorg.highwire.dtl.DTLVardef@1c2cb22_HPS_FORMAT_FIGEXP M_FIG C_FIG O_LIHippodamia convergens can tolerate freezing at high subzero temperatures C_LIO_LIMating behaviour of males is normal after chilling or freezing C_LIO_LICryoprotectant accumulation may support overwintering survival C_LI

zoology↗

bioRxiv2020

Hnrnpul1 loss of function affects skeletal and limb development

Mutations in RNA binding proteins can lead to pleiotropic phenotypes including craniofacial, skeletal, limb and neurological symptoms. Heterogeneous Nuclear Ribonucleoproteins (hnRNPs) are involved in nucleic acid binding, transcription and splicing through direct binding to DNA and RNA, or through interaction with other proteins in the spliceosome. We show a developmental role for Hnrnpul1 in zebrafish, resulting in reduced craniofacial tendon length, severe adult-onset scoliosis and reduced fin size. We demonstrate a role of Hnrnpul1 in alternative splicing and transcriptional regulation using RNA sequencing. Given its cross-species conservation and role in splicing it would not be surprising if it had a role in human development but the developmental role of this gene in humans has not been explored. Whole exome sequencing detected a frameshift variant in HNRNPUL1 in two siblings with congenital limb malformations which remain variants of unknown significance. Zebrafish Hnrnpul1 mutants suggest an important developmental role of hnRNPUL1 and provide motivation for exploring potential conservation of ancient regulatory circuits involving hnRNPUL1 in human development.

developmental biology↗