Whole-cell response to nitrogen deprivation in the diatomPhaeodactylum tricornutum

Abstract

HighlightAn integrated transcriptomics and metabolomics analysis of the nitrogen-deprivation response in the diatom Phaeodactylum tricornutum uncovered remobilization of internal nitrogen-containing resources, and remodelling of carbon and lipid structures.

Nitrate Reductase Knockout Uncouples Nitrate Transport from Nitrate Assimilation and Drives Repartitioning of Carbon Flux in a Model Pennate Diatom

“…Elevated expression of NR cohort genes after the addition of NO 3 2 is consistent with earlier studies in Arabidopsis (Scheible et al, 1997;Wang et al, 2000), where the addition of NO 3 2 was linked to increases both in uptake rates for NO 3 2 and in expression of NR and the genes involved in N-assimilation ( Figures 7A and 7C). Induced expression of the cohort in response to N-stress is also in agreement with previously described results in Arabidopsis thaliana and P. tricornutum (Alipanah et al, 2015;Glass et al, 2002;Levitan et al, 2015;Scheible et al, 2004;Wang et al, 2000Wang et al, , 2004. In NR-KO14 cells, the patterns of gene expression were atypical.…”

“…Shortly after NO 3 2 is introduced to NR-KO14 cells, expression levels of key functional and metabolic gene clusters indirectly related to N-assimilation are sharply downregulated. Despite ample extra-and intracellular NO 3 2 , transcript profiles for these clusters respond similarly to those observed in wild-type cells under N-stress (Alipanah et al 2015;Bender et al, 2014;Juergens et al, 2015;Levitan et al, 2015;Schmollinger at al., 2014). However, in contrast to wild-type cells which gradually acclimate to a dwindling supply of N-product, the response in NR-KO14 cells is quite rapid.…”

“…Since their expression is not dependent on supply of de novo N, or a lack thereof, it may be driven instead by the availability of key substrates, including 2OG and NH 3 + ; the former originating from possible mitochondrial or chloroplast-derived sources of plastidic ACOAT, or from alanine/ aspartate transaminase activity (Nunes-Nesi et al, 2010), and the latter arising from GLDH-mediated deamination of scavenged glutamate (Alipanah et al, 2015). Indeed, expression profiles of genes encoding ACOAT, unCPS, GLDH, and ICDH (Supplemental Figures 5D to 5F and 11B) are more similar to the upstream NR cohort genes and support their substantive links to N-assimilation and C-metabolism.…”

“…Much recent work has focused both on characterizing the genes and metabolic pathways that induce lipid biosynthesis and on identifying routes and regulators that could be harnessed to substantially increase TAG production without negatively affecting growth (Alipanah et al, 2015;Ge et al, 2014;Hildebrand et al, 2012;Levitan et al, 2015;Radakovits et al, 2010;Trentacoste et al, 2013;Yang et al, 2013;Yoon et al, 2012). Deleterious impacts of NO 3 2 depletion include reduction of photosynthetic capacity, C-fixation, and N-assimilation and cessation of growth (Alipanah et al, 2015;Bender et al, 2014;Hockin et al, 2012;Syrett et al, 1986;Turpin, 1991).…”

Profiling of the Early Nitrogen Stress Response in the Diatom Phaeodactylum tricornutum Reveals a Novel Family of RING-Domain Transcription Factors

“…Because of the inherent economic potential, several studies have investigated nitrogen starvation in P. tricornutum and T. pseudonana (Hockin et al, 2012;Valenzuela et al, 2012;Yang et al, 2013;Alipanah et al, 2015;Levitan et al, 2015). The most prevalent finding from the transcriptome analyses in these studies was that the accumulation of lipids appeared to be a consequence of the remodeling of central metabolism.…”