Crystal Structure of Diedel, a Marker of the Immune Response of Drosophila melanogaster

Background: The Drosophila melanogaster gene CG11501 is up regulated after a septic injury and was proposed to act as a negative regulator of the JAK/STAT signaling pathway. Diedel, the CG11501 gene product, is a small protein of 115 residues with 10 cysteines. Methodology/Principal Findings: We have produced Diedel in Drosophila S2 cells as an extra cellular protein thanks to its own signal peptide and solved its crystal structure at 1.15 A ˚ resolution by SIRAS using an iodo derivative. Diedel is composed of two sub domains SD1 and SD2. SD1 is made of an antiparallel b-sheet covered by an a-helix and displays a ferredoxin-like fold. SD2 reveals a new protein fold made of loops connected by four disulfide bridges. Further structural analysis identified conserved hydrophobic residues on the surface of Diedel that may constitute a potential binding site. The existence of two conformations, cis and trans, for the proline 52 may be of interest as prolyl peptidyl isomerisation has been shown to play a role in several physiological mechanisms. The genome of D. melanogaster contains two other genes coding for proteins homologous to Diedel, namely CG43228 and CG34329. Strikingly, apart from Drosophila and the pea aphid Acyrthosiphon pisum, Diedel-related sequences were exclusively identified in a few insect DNA viruses of the Baculoviridae and Ascoviridae families. Conclusion/Significance: Diedel, a marker of the Drosophila antimicrobial/antiviral response, is a member of a small famil

Analyses of genome architecture and gene expression reveal novel candidate virulence factors in the secretome of Phytophthora infestans

<p>Abstract</p> <p>Background</p> <p><it>Phytophthora infestans </it>is the most devastating pathogen of potato and a model organism for the oomycetes. It exhibits high evolutionary potential and rapidly adapts to host plants. The <it>P. infestans </it>genome experienced a repeat-driven expansion relative to the genomes of <it>Phytophthora sojae </it>and <it>Phytophthora ramorum </it>and shows a discontinuous distribution of gene density. Effector genes, such as members of the RXLR and Crinkler (CRN) families, localize to expanded, repeat-rich and gene-sparse regions of the genome. This distinct genomic environment is thought to contribute to genome plasticity and host adaptation.</p> <p>Results</p> <p>We used <it>in silico </it>approaches to predict and describe the repertoire of <it>P. infestans </it>secreted proteins (the secretome). We defined the "plastic secretome" as a subset of the genome that (i) encodes predicted secreted proteins, (ii) is excluded from genome segments orthologous to the <it>P. sojae </it>and <it>P. ramorum </it>genomes and (iii) is encoded by genes residing in gene sparse regions of <it>P. infestans </it>genome. Although including only ~3% <it>of P. infestans </it>genes, the plastic secretome contains ~62% of known effector genes and shows >2 fold enrichment in genes induced <it>in planta</it>. We highlight 19 plastic secretome genes induced <it>in planta </it>but distinct from previously described effectors. This list includes a trypsin-like serine protease, secreted oxidoreductases, small cysteine-rich proteins and repeat containing proteins that we propose to be novel candidate virulence factors.</p> <p>Conclusions</p> <p>This work revealed a remarkably diverse plastic secretome. It illustrates the value of combining genome architecture with comparative genomics to identify novel candidate virulence factors from pathogen genomes.</p