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

The ecological prominence of diatoms in the ocean environment largely results from their superior competitive ability for dissolved nitrate (NO 3 -). To investigate the cellular and genetic basis of diatom NO 3 - assimilation, in this paper we generated a knockout in the nitrate reductase gene (NR-KO) of the model pennate diatom Phaeodactylum tricornutum. In NR-KO cells, N-assimilation was abolished although NO 3 - transport remained intact. Unassimilated NO 3 - accumulated in NR-KO cells, resulting in swelling and associated changes in biochemical composition and physiology. Elevated expression of genes encoding putative vacuolar NO 3 - chloride channel transporters plus electron micrographs indicating enlarged vacuoles suggested vacuolar storage of NO 3 -. Triacylglycerol concentrations in the NR-KO cells increased immediately following the addition of NO 3 -, and these increases coincided with elevated gene expression of key triacylglycerol biosynthesis components. Simultaneously, induction of transcripts encoding proteins involved in thylakoid membrane lipid recycling suggested more abrupt repartitioning of carbon resources in NR-KO cells compared with the wild type. Conversely, ribosomal structure and photosystem genes were immediately deactivated in NR-KO cells following NO 3 - addition, followed within hours by deactivation of genes encoding enzymes for chlorophyll biosynthesis and carbon fixationmore » and metabolism. Finally, N-assimilation pathway genes respond uniquely, apparently induced simultaneously by both NO 3 - replete and deplete conditions.« less
Authors:
ORCiD logo [1] ;  [2] ;  [1] ;  [1] ; ORCiD logo [1] ; ORCiD logo [1] ; ORCiD logo [3] ;  [4] ;  [3] ;  [4] ;  [1] ; ORCiD logo [2]
  1. J. Craig Venter Inst., La Jolla, CA (United States). Microbial and Environmental Genomics
  2. J. Craig Venter Inst., La Jolla, CA (United States). Microbial and Environmental Genomics; Univ. of California, San Diego, CA (United States). Integrative Oceanography Division. Scripps Inst. of Oceanography
  3. Washington Univ., St. Louis, MO (United States). Dept. of Biology
  4. Ecole Normale Superieure, Paris (France). Inst. of Biology of the Ecole Normale Superieure
Publication Date:
Grant/Contract Number:
SC0008593; SC0006719; MCB-1024913; GBMF3828
Type:
Accepted Manuscript
Journal Name:
Plant Cell
Additional Journal Information:
Journal Volume: 29; Journal Issue: 8; Journal ID: ISSN 1040-4651
Publisher:
American Society of Plant Biologists
Research Org:
J. Craig Venter Inst., La Jolla, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23); National Science Foundation (NSF); Gordon and Betty Moore Foundation (United States)
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES
OSTI Identifier:
1423789