The availability of the full Drosophila genomic DNA sequence prompts the development of a method to efficiently obtain mutations in genes of interest identified by their sequence homologies or biochemically. To date, molecularly characterized mutations have been generated in around 6000 of the ∼15,000 annotated fly genes, of which around one-third are essential for viability. To obtain mutations in essential and nonessential genes of interest, we took a reverse genetics approach, based on the large-scale detection of point mutations by Cel-I-mediated heteroduplex cleavage. A library of genomic DNA from 2086 EMS-mutagenized lines was established. The library was screened for mutations in three genes. A total of 6.1 Mb were screened, and 44 hits were found in two different mutagenesis conditions. Optimal conditions yielded an average of one mutation every 156 kb. For an essential gene tested, five of 25 mutations turned out to cause lethality, confirming that EMS mutagenesis leads to high frequency of gene inactivation. We thereby established that Cel-I-mediated TILLING can be used to efficiently obtain mutations in genes of interest in Drosophila

This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits distribution, and reproduction in any medium, provided the original author and source are credited. This license does not permit commercial exploitation without specific permission.In vertebrates, seven signal transducer and activator of transcription (STAT) proteins bind to palindromic sites separated by spacers of two or three nucleotides (STAT1), four nucleotides (STAT6) or three nucleotides (STAT2 to STAT5a/b). This diversity of binding sites provides specificity to counter semiredundancy and was thought to be a recent evolutionary acquisition. Here, we examine the natural DNA-binding sites of the single Drosophila Stat and show that this is not the case. Rather, Drosophila Stat92E is able to bind to and activate target gene expression through both 3n and 4n spaced sites. Our experiments indicate that Stat92E has a higher binding affinity for 3n sites than for 4n sites and suggest that the levels of target gene expression can be modulated by insertion and/or deletion of single bases. Our results indicate that the ancestral STAT protein had the capacity to bind to 3n and 4n sites and that specific STAT binding preferences evolved with the radiation of the vertebrate STAT family.

Unravelling the molecular mechanisms that govern cell migration is of great importance towards understanding both normal embryogenesis and physiological and pathological processes occurring in the adult. Migration of border cells (BCs) during Drosophila oogenesis provides a simple and attractive model in which to address this problem. Here, we show that the molecular chaperone Hsp70 is required for BC migration. Thus, BCs lacking all Hsp70 genes present in the fly genome fail to reorganize their actin cytoskeleton, resulting in migration defects. Similar defects are found when the Hsp70 co-chaperone DnaJ-1, the Drosophila homolog of the human Hsp40, is overexpressed specifically in BCs. In addition, we provide biochemical and genetic evidence for an interaction between DnaJ-1 and PDGF/VEGF receptor (PVR), which is also required for actin-mediated BC migration. Furthermore, our results showing that PVR also interacts genetically with Hsp70 suggest that a mechanism by which the DnaJ-1/Hsp70 chaperone complex regulates BC migration is by modulating PVR function.