The Dorsal-related immunity factor (Dif) can define the dorsal-ventral axis of polarity in the Drosophila embryo

Abstract

In Drosophila embryos, dorsal-ventral polarity is defined by a signal transduction pathway that regulates nuclear import of the Dorsal protein. Dorsal protein's ability to act as a transcriptional activator of some zygotic genes and a repressor of others defines structure along the dorsal-ventral axis. Dorsal is a member of a group of proteins, the Rel-homologous proteins, whose activity is regulated at the level of nuclear localization. Dif, a more recently identified Drosophila Rel-homologue, has been proposed to act as a mediator of the immune response in Drosophila. In an effort to understand the function and regulation of Rel-homologous proteins in Drosophila, we have expressed Dif protein in Drosophila embryos derived from dorsal mutant mothers. We found that the Dif protein was capable of restoring embryonic dorsal-ventral pattern elements and was able to define polarity correctly with respect to the orientation of the egg shell. This, together with the observation that the ability of Dif to restore a dorsal-ventral axis depended on the signal transduction pathway that normally regulates Dorsal, suggests that Dif protein formed a nuclear concentration gradient similar to that seen for Dorsal. By studying the expression of Dorsal target genes we found that Dif could activate the zygotic genes that Dorsal activates and repress the genes repressed by Dorsal. Differences in the expression of these target genes, as well as the results from interaction studies carried out in yeast, suggest that Dif is not capable of synergizing with the basic helix-loop-helix transcription factors with which Dorsal normally interacts, and thereby lacks an important component of Dorsal-mediated pattern formation.

A mosaic analysis in Drosophila fat body cells of the control of antimicrobial peptide genes by the Rel proteins Dorsal and DIF

“…Only the dl gene, however, is expressed in the early embryo where it regulates dorsoventral patterning. Recently, Stein et al (1998) have shown that maternal expression of dif can partially rescue embryos from the consequences of a dl mutation, suggesting that DIF can partially substitute for Dl in this context. Furthermore, these experiments showed that dldeficient embryos rescued by dif exhibited dorsoventral polarity, which indicates that in these conditions DIF remained sensitive to the dorsoventral signaling cascade transmitted through Tl.…”

“…Only the dl gene, however, is expressed in the early embryo where it regulates dorsoventral patterning. Recently, Stein et al . (1998) have shown that maternal expression of dif can partially rescue embryos from the consequences of a dl mutation, suggesting that DIF can partially substitute for Dl in this context.…”

“…Furthermore, these experiments showed that dl ‐deficient embryos rescued by dif exhibited dorsoventral polarity, which indicates that in these conditions DIF remained sensitive to the dorsoventral signaling cascade transmitted through Tl. Nevertheless, Dl and DIF are not totally interchangeable in this context, as dl − embryos were only partially rescued by expression of the dif gene (Stein et al ., 1998). This observation is consistent with in vitro data in the immune system showing that DIF and Dl have somewhat different transactivating capabilities and do not bind κB‐motifs present in the upstream regions of the genes encoding Cecropin and Diptericin with the same affinities (Petersen et al ., 1995; Gross et al ., 1996).…”

An ancient defense system eliminates unfit cells from developing tissues during cell competition

“…1B and table S1). Spz is a secreted cytokine and a ligand for the Toll receptor in innate immunity and in embryonic dorsoventral patterning (30,(33)(34)(35). However, RNA interference (RNAi)-mediated knockdown of Toll itself (Toll-1) had little effect on competition (fig.…”

The neurodevelopmental transcriptome of theDrosophila melanogastermicrocephaly geneabnormal spindlereveals a role for temporal transcription factors and the immune system in regulating brain size

“…It also remains an open question as to whether the NF-ΚB factors have other transcriptional targets unrelated to the immune response that could be responsible. This is especially true for dif , who has additional developmental patterning roles during embryogenesis [53] and whose brains are ∼10% larger than wildtype.…”