Project description:Color vision in Drosophila is mediated by photoreceptors R7 and R8, which express various combinations of opsins Rh3, Rh4, Rh5 and Rh6 depending on their cellular identity. Most ommatidia are classified as either “pale” or “yellow” subtypes with pale ommatidia coordinately expressing Rh3 and Rh5—in R7 and R8 cells respectively—while yellow express Rh4 and Rh6. Subtype identity is established initially in R7 photoreceptors via a stochastic mechanism then transmitted to the R8 via an inductive signal to ensure paired opsin expression. To identify factors that may be involved in this process, we used RNA-Seq to detect genes that are differentially expressed in sevenless mutant retinas at 40 hours after puparium formation. Since loss of sevenless prevents R7 recruitment and specification, we reasoned that this approach would allow us to identify genes that are enriched in R7 cells during this critical time point. Furthermore, since it has previously been established that in the absence of R7 most R8s will adopt the yellow Rh6-expressing identity, this gives us the opportunity to identify genes which may inductive mechanism occurring in R8 cells.
Project description:Investigation of whole genome gene expression level changes in a Sinorhizobium meliloti 1021 rpoH1 rpoH2 double mutant, compared to the wild-type strain. The mutations engineered into this strain render it deficient in symbiotic nitrogen fixation. The mutants analyzed in this study are further described in Mitsui, H, T. Sato, Y. Sato, and K. Minamisawa. 2004. Sinorhizobium meliloti RpoH1 is required for effective nitrogen-fixing symbiosis with alfalfa. Mol Gen Genomics 271:416-425.
Project description:Many bacteria, often associated with eukaryotic hosts and of relevance for biotechnological applications, harbor a multipartite genome composed of more than one replicon. Biotechnologically relevant phenotypes are often encoded by genes residing on the secondary replicons. A synthetic biology approach to developing enhanced strains for biotechnological purposes could therefore involve merging pieces or entire replicons from multiple strains into a single genome. Here we report the creation of a genomic hybrid strain in a model multipartite genome species, the plant-symbiotic bacterium Sinorhizobium meliloti. We term this strain as cis-hybrid, since it is produced by genomic material coming from the same species' pangenome. In particular, we moved the secondary replicon pSymA (accounting for nearly 20% of total genome content) from a donor S. meliloti strain to an acceptor strain. The cis-hybrid strain was screened for a panel of complex phenotypes (carbon/nitrogen utilization phenotypes, intra- and extracellular metabolomes, symbiosis, and various microbiological tests). Additionally, metabolic network reconstruction and constraint-based modeling were employed for in silico prediction of metabolic flux reorganization. Phenotypes of the cis-hybrid strain were in good agreement with those of both parental strains. Interestingly, the symbiotic phenotype showed a marked cultivar-specific improvement with the cis-hybrid strains compared to both parental strains. These results provide a proof-of-principle for the feasibility of genome-wide replicon-based remodelling of bacterial strains for improved biotechnological applications in precision agriculture.