Open AccessRegulation of Indole-3-Acetic Acid Biosynthetic Pathways in Carrot Cell Cultures
Author(s) -
Lech Michalczuk,
David M. Ribnicky,
Todd J. Cooke,
Jerry D. Cohen
Publication year - 1992
Publication title -
plant physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.554
H-Index - 312
eISSN - 1532-2548
pISSN - 0032-0889
DOI - 10.1104/pp.100.3.1346
Subject(s) - callus , tryptophan , indole 3 acetic acid , biosynthesis , biochemistry , auxin , embryo , indole test , daucus carota , biology , tryptamine , somatic embryogenesis , chemistry , tissue culture , amino acid , botany , in vitro , microbiology and biotechnology , gene , enzyme
2,4-Dichlorophenoxyacetic acid (2,4-D) promotes the accumulation of tryptophan-derived indole-3-acetic acid (IAA) in carrot cell cultures during callus proliferation by a biosynthetic pathway that is apparently not active during somatic embryo formation. The effects of 2,4-D were examined by measuring the isotopic enrichment of IAA due to the incorporation of stable isotope-labeled precursors (deuterium oxide, [(15)N]indole, and (2)H(5)-l-tryptophan). Enrichment of IAA from deuterium oxide is similar in both cultured hypocotyls and cell suspension cultures in the presence and absence of 2,4-D, despite the large differences in absolute IAA concentrations. The enrichment of IAA due to the incorporation of [(15)N]indole is also similar in callus proliferating in the presence of 2,4-D and in embryos developing in the absence of 2,4-D. The incorporation of (2)H(5)-l-tryptophan into IAA, however, is at least 7-fold higher in carrot callus cultures proliferating in the presence of 2,4-D than in embryos developing in the absence of 2,4-D. Other experiments demonstrated that this differential incorporation of (2)H(5)-l-tryptophan into IAA does not result from differential tryptophan uptake or its subsequent compartmentation. Thus, it appears that differential pathways for IAA synthesis operate in callus cultures and in developing embryos, which may suggest that a relationship exists between the route of IAA biosynthesis and development.