Submitted to: European Journal of Entomology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/29/2004
Publication Date: 6/25/2004
Citation: Yocum, G.D. 2004. Environmental regulation of the purine synthesis enzyme purH transcript during adult diapause in Leptinotarsa decemlineata (Coleoptera: Chrysomelidae). European Journal of Entomology. 101(2):199-203. Interpretive Summary: Environmental conditions required for reproduction and development are normally restricted to only a small part of the year, especially in the temperate zones where organisms must survive winter with its associated low temperatures, low humidity and lack of food. To survive these recurring and predictable periods of environmental stress, a wide spectrum of organisms employs some form of dormancy (known in insects as diapause). Organisms in dormancy are characterized by suppressed metabolism and increased tolerance to environmental stresses. Purine serves as the basis for metabolic energy currency as well chemical storage of biological information. The purine synthesis enzyme purH was isolated from the Colorado potato beetle and its expression was examined in diapausing and nondiapausing beetles. PurH is highly expressed in nondiapausing and prediapausing beetles. PurH expression decreases significantly after 20 days in diapause. The decrease in purH expression could act to limit the de novo synthesis of purine needed for development and energy metabolism during diapause, suggesting an intriguing possibility for a mechanism controlling metabolic rate during diapause.
Technical Abstract: A 1962 bp cDNA clone of 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/IMP cyclohydrolase (purH) was isolated from diapausing adults of Leptinotarsa decemlineata using RT-PCR and 3' and 5'-RACE. The probe generated from this clone hybridized to a transcript approximately 1960 bp in length on northern blots. The clone encodes for a deduced protein 594 amino acids in length with 73% identity, 83% similarity to purH from Drosophila melanogaster. Northern blot analysis determined that L. decemlineata purH (LdpurH) was downregulated in diapausing beetles. Developmental studies revealed that LdpurH is expressed at nearly constant high levels in both nondiapausing and prediapause adults. LdpurH expression during the first 20 days of diapause is equivalent to that seen in nondiapausing beetles, after which expression decreases. The decrease in purH expression could act to limit the de novo synthesis of purine needed for development and energy metabolism during diapause.