Metabolism and gene expression during diapause in athropods

Arthropods may enter diapause to escape environmental insult. Diapause is an endogenously controlled dormant state defined by developmental arrest and species-specific physiological changes (e.g., metabolic depression and upregulation of compounds that protect cell structure and function). Although physiological changes have been documented for a number of species in diapause, biochemical and molecular regulation of diapause remains largely unexplained. Aerobic metabolism in diapause, Artemia franciscana, embryos is reduced up to 92 % compared with post-diapause embryos. Differences in isolated mitochondria are insufficient to account for respiratory depression because mitochondria in diapause embryos are structurally similar to mitochondria in post-diapause embryos. Respiratory control ratios and P:O flux ratios of mitochondria from diapause embryos are equal to or higher than those of mitochondria from post-diapause embryos. State 3 and state 4 respiration rates on pyruvate are equivalent in the two stages, and mitochondria isolated from diapause embryos show a moderate, 15-27 % reduction with succinate. Cytochrome c oxidase activity is 53 % lower in diapause embryos, but the minimal impact on mitochondrial respiration appears to be due to the 31 % excess of COX capacity in these embryos. Allonemobius socius embryos enter diapause 3-4 d post-oviposition as indicated by their morphology and DNA embryo-1. There is not an acute downregulation of metabolism during diapause in this species. Diapause embryos consume O2 at the same rate as morphologically similar non-diapause embryos. Diapause and non-diapause embryos exhibit unusually high [AMP]/[ATP] and low [ATP]/[ADP] during early embryogenesis, suggesting that these embryos may be hypoxic early in development. However, superfusing 3 d embryos with O2 enriched air only partially relieves the hypoxic state, which indicates the unusual energy status is an ontogenetic feature not fully explained by oxygen limitation. Subtractive hybridization and qPCR identified 6 genes predicted to regulate diapause entry in A. socius. Reptin, TFDp2, CYP450, AKR are significantly upregulated in pre-diapause embryos, and ACLY and Capthesin B-like protease are downregulated compared to non-diapause embryos. The need for genes upregulated in pre-diapause embryos appears to be transient as these genes are substantially downregulated 10 d after diapause entry. Taken together, these studies provide an integrative examination of mechanisms underlying diapause entry in arthropods

A study of the effects of the juvenile hormone analogue methoprene on the intermediary metabolism of the African migratory locust

Insect juvenile hormone (JH) regulates the growth and development of insects. Synthetic analogues of JH (JHAs) have been used as agents of pest control, disrupting the metamorphosis of insects. The purpose of the present study was to determine physiological and biochemical effects of methoprene, a commercial JHA, on certain organs and tissues of the African migratory locust (Locusta mi- gratoria migratorioides, phase gregaria). Methoprene was topically applied to newly moulted, fifth (final) instar larvae and the subsequent development of the animals was followed. Cytological development of fat body and dorsal longitudinal flight muscle was studied by light and electron microscopy. Fat body cells of control insects were synthetically active early in the fifth instar, and stored lipid and glycogen in the latter half of the instar. Fat bodies of 8-day old adults were sexually dimorphic, female cells showing high levels of RNA and protein synthesis while male cells were filled with lipid and glycogen stores. Methoprene treatment stimulated the synthetic activity of the cells in fifth instar and adult stadia, especially in female tissue. Cell nuclei were abnormally enlarged, suggesting increased ploidy levels. Levels of lipid and carbohydrate were measured in fat body and haemolymph but methoprene had no obvious effect on them, nor on glycogen phosphorylase activity. However, the JHA affected rates of incorporation of [(^14)C]glucose into fat body lipids during the first four days of the fifth instar. Separation of haemolymph proteins by gel electrophoresis revealed an extra protein band in the blood of treated female locusts from the middle of the fifth instar onwards. The same band appeared in the blood of control females only when they reached sexual maturity. Methoprene treatment disrupted normal development of dorsal longitudinal flight muscles during the fifth instar and early adult life. The JHA reduced muscle fibre growth but seemed to accelerate myofibril and mitochondrial differentiation in the fifth instar. Treatment also inhibited formation of interfibrillar tracheoles and caused disruption of the myofilaments and sarcoplasmic reticulum in adult muscle. Mitochondria were isolated from flight muscles of mature adults and their respiratory metabolism was measured using an oxygen electrode. Mitochondria from control animals showed high rates of oxygen consumption and good respiratory control. Mitochondria from treated locusts had poor respiratory control and low respiratory rates. Similar results were obtained by in vitro applications of methoprene or juvenile hormone to mitochondria

The Effects of Potassium Bromide on Biochemical Contents of the Fat Body and Haemolymph of Crossbreed Races of the Silkworm, Bombyx mori L.

Oral supplementation with potassium bromide (10, 20 and 40 ?g/ml) to fifth instar larvae of CSR2, CSR4 and CSR2xCSR4 crossbreed races of the silkworm, Bombyx mori resulted in a significant increase in the fat body glycogen in all the treated groups and in all the three races of the silkworm, B. mori. The fat body protein content was increased with 20 and 40 ?g/ml treated groups in CSR2 and CSR4 races and in all the treated groups in CSR2xCSR4 cdrossbreed race of the silkworm, B. mori. However, there was a decrease in fat body protein with 10 ?g/ml treated groups in CSR2 and CSR4 races. There was a significant increase in the haemolymph trehalose with 10 ?g/ml in CSR2 race, in all the treated groups in CSR4 race and with 20 and 40 ?g/ml treated groups in CSR2xCSR4 crossbreed race when compared over the respective carrier controls. There was also a significant increase in the haemolymph protein treated with 20 and 40 ?g/ml in CSR2 race, with 10 and 20 ?g/ml in CSR4 race and in all the treated groups in CSR2xCSR4 crossbreed race when compared over the respective carrier controls. There was a significant increase in the fat body total lipids with all the treated groups and in all the three races of the silkworm, but there was a significant decrease with 40 ?g/ml treated group in CSR2xCSR4 race of the silkworm, B. mori when compared over the respective carrier controls. These results indicated that the biochemical contents of the fat body and haemolymph to potassium bromide showed good response in all the three races of the silkworm, Bombyx mori L