Juvenile hormone-regulated locust vitellogenin genes: Lack of expression after transfer intoDrosophila

Abstract

In Locusta rnigratoria, vitellogenin (Vg) is normally produced only in adult female fat body under stimulation by juvenile hormone (JH). This permits study of a) programming of genes for expression and b) modulation of expression by JH. From L. rnigratoria genomic libraries, two Vg genes (A and B) have been cloned. Coding regions encompass 10-12 kbases of DNA, contain introns, and hybridize with 6,300 nucleotide mRNAs. Although the 5'-exons, coding for signal peptides, are similar in sequence, the remaining coding sequences have distinct restriction maps and show no crosshybridization. Upstream DNA from the two genes has some sequence similarity, corresponding to potential regulatory regions. Dot hybridization assays of mRNAs A and B in locust fat body after induction by methoprene show coordinate expression of the two Vg genes and also a third, unidentified JH-regulated gene. In the hope of providing a system for identification of control sequences, P element-mediated transformation has been used to transfer locust DNA into Drosophila. From Vg gene B, a central block was deleted, to give a mini-Vg gene comprising 5' and 3' terminal coding sequences plus upstream flanking DNA. This was incorporated into the P element vector Carnegie 20 and injected into Drosophila embryos. Three transformed fly lines were obtained in which the locust mini-Vg gene was integrated at different chromosomal sites. On Northern blots of fly RNA, however, no expression of the locust sequences could be detected, even though the accompanying rosy gene was expressed. This suggests that the locust regulatory sequences were not recognized in Drosophila, and current effort i s directed toward developing a homologous locust transformation system for expression assay of cloned JH-regulated genes.

Cloning and 5′ End Nucleotide Sequences of Two Juvenile Hormone-Inducible Vitellogenin Genes of the African Migratory Locust

“…Similarities between upstream flanking sequences of the locust Vg genes, which are coordinately expressed (Wyatt et al, 1986), may reflect such a role. In the proximal region of the promoter, both genes have TATA boxes surrounded by GC-rich regions but without extensive sequence identity.…”

Priming effect in gene activation by juvenile hormone in locust fat body

“…Analysis of the molecular basis for hormonal control of transcription requires a system for assaying the effects of addition, removal, or modification of components. After disappointing results with a variety of whole-cell transfection systems (Wyatt et al, 1986;Mathi et al, 1991;Walker et al, 1991;unpublished data), we have found that soluble extracts from fat body nuclei are capable of faithful, regulated transcription from a locust promoter/enhancer system. Initial results, described above, have demonstrated transcription from the jhp21 promoter in extracts from JH-exposed, but not from JH-deprived fat body, thus directly demonstrating the JH-induced accumulation of a specific transcription factor.…”

Differential Gene Expression in Insects: Transcriptional Control

“…For example, no detectable expression existed in D. melanogaster after P-element transformation of a portion of the locust vitellogenin gene along with 5′-end-flanking DNA from the gene (181). In spite of the evident problems, successes have occured using heterologous expression undoubtedly because DNA regulatory elements and factors are often highly conserved in evolution.…”