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Linking the Cytosolic Phenylalanine Pathway, and the Auxin Biosynthetic Pathway
Author(s) -
Garcia Alekzander,
Qian Yichun,
Lynch Joseph,
Dudareva Natalia
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.628.1
Subject(s) - chorismate mutase , biochemistry , shikimate pathway , auxin , aromatic amino acids , tryptophan , biosynthesis , phenylalanine , cytosol , metabolic pathway , plastid , tyrosine , amino acid , biology , enzyme , chemistry , gene , chloroplast
The shikimate pathway is a biosynthetic pathway that leads to the production chorismate, the precursor of the aromatic amino acids. In production of phenylalanine (Phe) and tyrosine (Tyr), chorismate is first converted to prephenate by the enzyme chorismate mutase. The predominantly expressed isoform of chorismate mutase (CM1) is located in the plastids; however, a second isoform (CM2) is present in the cytosol, but the role of this cytosolic isoform in plants is still unknown. Preliminary results from Petunia hybrida , cv Mitchell flowers that overexpress CM2 suggest a possible decrease in plastid content. As auxin is known to inhibit the formation of leucoplasts and amyloplasts, we hypothesize a metabolic link between cytosolic Phe production via CM2 and the tryptophan‐dependent auxin biosynthetic pathway. In this study, CM2 expression in the previously developed overexpression lines was analyzed by qRT‐PCR. Despite confirmed overexpression of the gene, downstream products Phe and total anthocyanins were decreased. In contrast, there was a significant increase of phenylpyruvate, the immediate precursor of Phe and an amino‐acceptor in auxin biosynthesis. Plastid content was quantified by starch assays and found to be decreased in flowers of CM2 overexpression lines. Finally, the auxin indole‐3‐pyruvic acid (IPA) and indole‐3‐acetic acid (IAA) were increased as compared to the wildtype. Our results demonstrate a connection between the tryptophan‐dependent auxin biosynthetic pathway and the CM2‐dependent cytosolic Phe biosynthetic pathway. Support or Funding Information NSF‐REU for Molecular and Biochemical Analysis of Proteins at Purdue University 2016