TY - JOUR
T1 - Regulation of indole-3-acetic acid biosynthetic pathways in carrot cell cultures
AU - Michalczuk, Lech
AU - Ribnicky, David M.
AU - Cooke, Todd J.
AU - Cohen, Jerry D.
PY - 1992/11
Y1 - 1992/11
N2 - 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, [15N]indole, and 2H5-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 [15N]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 2H5-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 2H5-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.
AB - 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, [15N]indole, and 2H5-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 [15N]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 2H5-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 2H5-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.
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U2 - 10.1104/pp.100.3.1346
DO - 10.1104/pp.100.3.1346
M3 - Article
C2 - 16653127
AN - SCOPUS:0000039131
SN - 0032-0889
VL - 100
SP - 1346
EP - 1353
JO - Plant physiology
JF - Plant physiology
IS - 3
ER -