The Su(var)3-7 protein is essential for fly viability, and several lines of evidence support its key importance in heterochromatin formation: it binds to pericentric heterochromatin, it potently suppresses variegation and it interacts with HP1. However, the mode of action of Su(var)3-7 is poorly understood. Here we investigate in vivo the consequences of increased Su(var)3-7 expression on fly viability and chromatin structure. A large excess of Su(var)3-7 induces lethality, whereas lower doses permit survival and cause spectacular changes in the morphology of polytene chromosomes in males, and to a lesser extent in females. The male X is always the most affected chromosome: it becomes highly condensed and shortened, and its characteristic banding pattern is modified. In addition, Su(var)3-7 was found over the complete length of all chromosomes. This event coincides with the appearance of heterochromatin markers such as histone H3K9 dimethylation and HP1 at many sites on autosomes and, more strikingly, on the male X chromosome. These two features are strictly dependent on the histone-methyltransferase Su(var)3-9, whereas the generalised localisation of Su(var)3-7 is not. These data provide evidence for a dose-dependent regulatory role of Su(var)37 in chromosome morphology and heterochromatin formation. Moreover they show that Su(var)3-7 expression is sufficient to induce Su(var)3-9-dependent ectopic heterochromatinisation and suggest a functional link between Su(var)3-7 and the histone-methyltransferase Su(var)3-9

The Drosophila protein SU(VAR)3-7 is essential for fly viability, chromosome structure, and heterochromatin formation. We report that searches in silico and in vitro for homologues of SU(VAR)3-7 were successful within, but not outside, the Drosophila genus. Protein sequence homology between the distant sibling species Drosophila melanogaster and Drosophila virilis is low, except for the general organization of the protein and three conserved motives: seven widely spaced zinc fingers in the N-terminal half and the BESS and BoxA motives in the C-terminal half of the protein. We have undertaken a fine functional dissection of SU(VAR)3-7 in vivo using transgenes encoding truncations of the protein. BESS mediates interaction of SU(VAR)3-7 with itself, and BoxA is required for specific heterochromatin association. Both are necessary for the silencing properties of SU(VAR)3-7. The seven zinc fingers, widely spaced over the N-terminal half of SU(VAR)3-7, are required for binding to polytene chromosomes. One finger is necessary and sufficient to determine the appropriate chromatin association of the C-terminal half of the protein. Conferring a function to each of the conserved motives allows us to better understand the mode of action of SU(VAR)3-7 in triggering heterochromatin formation and subsequent genomic silencing.

Summary. The existence of Ca2+-dependent protease II in crude extracts of Neurospora crassa and Uromyces appendiculatus was demonstrated by immunoblotting using specific antibodies. In both extracts two immunoreacting bands were observed. The molecular mass of the major band in N. crassa corresponded to 37 kDa, while that in U. appendiculatus was 43 kDa, similar to that previously reported for Allomyces arbuscula. Immunofluorescence of the enzyme was predominantly localized in the apical regions of germlings and growing hyphae, suggesting a functional role for the enzyme in hyphal growth.

In the past decade, digital technologies have started to profoundly influence healthcare systems. Digital selftracking has facilitated more precise epidemiological studies, and in the field of nutritional epidemiology, mobile apps have the potential to alleviate a significant part of the journaling burden by, for example, allowing users to record their food intake via a simple scan of packaged products' barcodes. Such studies thus rely on databases of commercialized products, their barcodes, ingredients, and nutritional values, which are not yet openly available with sufficient geographical and product coverage. In this paper, we present FoodRepo (https://www.foodrepo.org), an open food repository of barcoded food items, whose database is programmatically accessible through an application programming interface (API). Furthermore, an open source license gives the appropriate rights to anyone to share and reuse FoodRepo data, including for commercial purposes. With currently more than 21,000 items available on the Swiss market, our database represents a solid starting point for large-scale studies in the field of digital nutrition, with the aim to lead to a better understanding of the intricate connections between diets and health in general, and metabolic disorders in particular.

The Su(var)3-7 gene, a haplo-suppressor and triplo-enhancer of position-effect variegation (PEV), encodes a zinc finger heterochromatin-associated protein. To understand the role of this protein in heterochromatin and genomic silencing, mutations were generated by homologous recombination. The donor fragment contained a yellow+ gene and 7.6 kb of the Su(var)3-7 gene inserted between two FRTs. The Su(var)3-7 sequence contained three stop codons flanking an I-SceI cut site located in the 5′ half of the gene. Using two different screening approaches, we obtained an allelic series composed of three mutant alleles. The three mutations are dominant suppressors of PEV. One behaves as a null mutation and results in a maternal-effect recessive lethal phenotype that can be rescued by a zygotic paternal wild-type gene. A P transposon zygotically expressing a Su(var)3-7 full-length cDNA also rescues the mutant phenotype. One hypomorphic allele is viable and the pleiotropic phenotype showed by adult flies indicates that rapidly and late dividing cells seem the most affected by reduced amounts of Su(var)3-7 protein. All three mutants were characterized at the molecular level. Each expresses a portion of the Su(var)3-7 protein that is unable to enter the nucleus and bind chromatin.