Most plant-sap feeding insects have obligate relationships with maternally transmitted bacteria. Aphids require their nutritional endosymbiont, Buchnera aphidicola, for the production of essential amino acids. Such endosymbionts are harbored inside of specialized insect cells called bacteriocytes. Here, we use comparative transcriptomics of bacteriocytes between two recently diverged aphid species, Myzus persicae and Acyrthosiphon pisum, to identify key genes that are important for the maintenance of their nutritional mutualism. The majority of genes with conserved expression profiles in M. persicae and A. pisum are for orthologs previously identified in A. pisum to be important for the symbiosis. However, asparaginase which produces aspartate from asparagine was significantly up-regulated only in A. pisum bacteriocytes, potentially because Buchnera of M. persicae encodes its own asparaginase enzyme unlike Buchnera of A. pisum resulting in Buchnera of A. pisum to be dependent on its aphid host for aspartate. One-to-one orthologs that explained the most amount of variation for bacteriocyte specific mRNA expression for both species includes a collaborative gene for methionine biosynthesis, multiple transporters, a horizontally transmitted gene, and secreted proteins. Finally, we highlight species-specific gene clusters which may contribute to host adaptations and/or accommodations in gene regulation to changes in the symbiont or the symbiosis.

Vitamin D is a steroid hormone that has been widely studied as a potential therapy for multiple sclerosis and other inflammatory disorders. Pre-clinical studies have implicated vitamin D in the transcription of thousands of genes, but its influence may vary by cell type. A handful of clinical studies have failed to identify an in vivo gene expression signature when using bulk analysis of all peripheral immune cells. We hypothesized that vitamin D’s gene signature would vary by immune cell type, requiring the analysis of distinct cell types. Multiple sclerosis patients (n = 18) were given high-dose vitamin D (10,400 IU/day) for six months as part of a prospective clinical trial (NCT01024777). We collected peripheral blood mononuclear cells from participants at baseline and again after six months of treatment. We used flow cytometry to isolate three immune cell types (CD4+ T-cells, CD19+ B-cells, CD14+ monocytes) for RNA microarray analysis and compared the expression profiles between baseline and six months. We identified distinct sets of differentially expressed genes and enriched pathways between baseline and six months for each cell type. Vitamin D’s in vivo gene expression profile in the immune system likely differs by cell type. Future clinical studies should consider techniques that allow for a similar cell-type resolution.