Developmental and environmental regulation of antifreeze proteins in the mealworm beetle Tenebrio molitor

Abstract

The yellow mealworm beetle, Tenebrio molitor, contains a family of small Cys-rich and Thr-rich thermal hysteresis proteins that depress the hemolymph freezing point below the melting point by as much as 5.5 8C (DT thermal hysteresis). Thermal hysteresis protein expression was evaluated throughout development and after exposure to altered environmental conditions. Under favorable growth conditions, small larvae (11±13 mg) had only low levels of thermal hysteresis proteins or thermal hysteresis protein message, but these levels increased 10-fold and 18-fold, respectively, by the final larval instar (. 190 mg), resulting in thermal hysteresis . 3 8C. Exposure of small larvae (11±13 mg) to 4 weeks of cold (4 8C) caused an < 20-fold increase in thermal hysteresis protein concentration, well in excess of the less than threefold developmental increase seen after 4 weeks at 22 8C. Exposure of large larvae (100±120 mg) to cold caused 12-fold and sixfold increases in thermal hysteresis protein message and protein levels, respectively, approximately double the maximum levels they would have attained in the final larval instar at 22 8C. Thus, thermal hysteresis increased to similar levels (. 4 8C) in the cold, irrespective of the size of the larvae (the overwintering stage). At pupation, thermal hysteresis protein message levels decreased . 20-fold and remained low thereafter, but thermal hysteresis activity decreased much more slowly. Exposure to cold did not reverse this decline. Desiccation or starvation of larvae had comparable effects to cold exposure, but surprisingly, short daylength photoperiod or total darkness had no effect on either thermal hysteresis or message levels. As all environmental conditions that caused increased thermal hysteresis also inhibited growth, we postulate that developmental arrest is a primary factor in the regulation of T. molitor thermal hysteresis proteins.

A Novel 43-kDa Protein as a Negative Regulatory Component of Phenoloxidase-induced Melanin Synthesis

“…A partial amino acid sequence of band 5 was identified as DAEESAEPTSGE-VIS, which showed no sequence homology with known proteins in the data base, and the function of this protein is not determined yet. The amino-terminal sequence of band 6 was determined as SDSDEVLEKVKSKHL, which perfectly matched with the Tenebrio desiccation protein that was reported to be engaged in developmental and environmental regulation of thermal hysteresis (28).…”

Activity and dormancy in relation to body water and cold tolerance in a winter-active springtail (Collembola)

“…It was postulated that thermal hysteresis is important for water retention in Tenebrio molitor larvae (Patterson & Duman, 1978). Further, Graham et al (2000) showed that desiccation had the same effect as cold exposure in increasing the level of thermal hysteresis in larvae of T. molitor. THPs were also found in summer-acclimatised oribatid mites (Phauloppia sp.…”

Characterization of a Subfamily of Beetle Odorant-binding Proteins Found in Hemolymph

“…Isoform Purification-Hemolymph (2.5 ml) was collected from T. molitor larvae reared under control conditions as described previously (20). Gel-exclusion chromatography and analytical HPLC were done as described by Liou et al (21) except that the gradient for HPLC was 10 -30% B (80% acetonitrile, 0.05% trifluoroacetic acid) in 10 min followed by 30 -50% B in 40 min.…”