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Title: Terpene metabolic engineering via nuclear or chloroplast genomes profoundly and globally impacts off-target pathways through metabolite signalling

The impact of metabolic engineering on nontarget pathways and outcomes of metabolic engineering from different genomes are poorly understood questions. Therefore, squalene biosynthesis genes FARNESYL DIPHOSPHATE SYNTHASE (FPS) and SQUALENE SYNTHASE (SQS) were engineered via the Nicotiana tabacum chloroplast (C), nuclear (N) or both (CN) genomes to promote squalene biosynthesis. SQS levels were similar to 4300-fold higher in C and CN lines than in N, but all accumulated similar to 150-fold higher squalene due to substrate or storage limitations. Abnormal leaf and flower phenotypes, including lower pollen production and reduced fertility, were observed regardless of the compartment or level of transgene expression. Substantial changes in metabolomes of all lines were observed: levels of 65-120 unrelated metabolites, including the toxic alkaloid nicotine, changed by as much as 32-fold. Profound effects of transgenesis on nontarget gene expression included changes in the abundance of 19 076 transcripts by up to 2000-fold in CN; 7784 transcripts by up to 1400-fold in N; and 5224 transcripts by as much as 2200-fold in C. Transporter-related transcripts were induced, and cell cycle-associated transcripts were disproportionally repressed in all three lines. Transcriptome changes were validated by qRT-PCR. In conclusion, the mechanism underlying these large changes likely involves metabolite-mediatedmore » anterograde and/or retrograde signalling irrespective of the level of transgene expression or end product, due to imbalance of metabolic pools, offering new insight into both anticipated and unanticipated consequences of metabolic engineering.« less
Authors:
 [1] ;  [1] ;  [2] ;  [2] ;  [2] ;  [3] ;  [1]
  1. Univ. of Pennsylvania, Philadelphia, PA (United States). School of Dental Medicine, Dept. of Biochemistry
  2. Univ. of Pennsylvania, Philadelphia, PA (United States). Dept. of Biology
  3. Texas A & M Univ., College Station, TX (United States). Dept. of Plant Pathology and Microbiology
Publication Date:
OSTI Identifier:
1240755
Grant/Contract Number:
R01 HL107904; R01 HL109442
Type:
Published Article
Journal Name:
Plant Biotechnology Journal
Additional Journal Information:
Journal Volume: 14; Journal Issue: 9; Journal ID: ISSN 1467-7644
Publisher:
Society for Experimental Biology; Association of Applied Biology
Research Org:
Univ. of Pennsylvania, Philadelphia, PA (United States)
Sponsoring Org:
USDOE Advanced Research Projects Agency - Energy (ARPA-E); National Institutes of Health (NIH)
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; 60 APPLIED LIFE SCIENCES; Secondary metabolism; retrograde/anterograde signalling; transgenic/transplastomic plants; squalene