AUTHOR=Frischkorn Kyle R. , Haley Sheean T. , Dyhrman Sonya T. 

TITLE=Transcriptional and Proteomic Choreography Under Phosphorus Deficiency and Re-supply in the N2 Fixing Cyanobacterium Trichodesmium erythraeum

JOURNAL=Frontiers in Microbiology

VOLUME=Volume 10 - 2019

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.00330

DOI=10.3389/fmicb.2019.00330

ISSN=1664-302X

ABSTRACT=The N2 fixing cyanobacterium Trichodesmium is a critically important organism in oligotrophic marine ecosystems, supplying ”new” nitrogen (N) to the otherwise N-poor tropical and subtropical regions where it occurs. Low concentrations of phosphorus (P) in these regions can constrain Trichodesmium distribution and N2 fixation rates. Physiological characterization of a single species in a mixed community can be challenging, and ‘omic approaches are increasingly important tools for tracking nutritional physiology in a taxon-specific manner. As such, studies examining the dynamics of gene and protein markers of physiology (e.g., nutrient stress) are critical for the application and interpretation of such ‘omic data in situ. Here we leveraged combined transcriptomics, proteomics, and enzyme activity assays to track the physiological response of T. erythraeum IMS101 to P deficiency and subsequent P resupply over 72 hours of sampling. P deficiency resulted in the differential gene expression, protein abundance, and enzyme activity that highlighted a synchronous shift in P physiology with increases in the transcripts and corresponding proteins for hydrolyzing organic phosphorus, taking up phosphate with higher affinity, and modulating intracellular P demand.  After P deficiency was alleviated, gene expression of these biomarkers was reduced to replete levels within 4 hours of P amendment. A number of these gene biomarkers were adjacent to putative pho-boxes and their expression patterns were similar to a sphR response regulator. Proteins products of the P deficiency biomarkers were slow to decline, with 84% of the original P deficient protein set still significantly differentially expressed after 72 hours. Alkaline phosphatase activity tracked with proteins for this enzyme. With the rapid turnover time of transcripts, they appear to be good biomarkers of a P stress phenotype, whereas proteins, with a slower turnover time, may better reflect cellular activities. These results highlight the importance of validating and pairing transcriptome and proteome data that can be applied to physiological studies of key species in situ.