Abscisic acid biosynthesis in leaves and roots of Xanthium strumarium

Journal Article · Sun Nov 01 04:00:00 EST 1987 · Plant Physiol.; (United States)

DOI:https://doi.org/10.1104/pp.85.3.726· OSTI ID:5403238

Creelman, R A; Gage, D A; Stults, J T; Zeevaart, J A.D.

Research on the biosynthesis of abscisic acid (ABA) has focused primarily on two pathways: (a) the direct pathway from farnesyl pyrophosphate, and (b) the indirect pathway involving a carotenoid precursor. The authors have investigated which biosynthetic pathway is operating in turgid and stressed Xanthium leaves, and in stressed Xanthium roots using long-term incubations in /sup 18/O/sub 2/. It was found that in stressed leaves three atoms of /sup 18/O from /sup 18/O/sub 2/ are incorporated into the ABA molecule, and that the amount of /sup 18/O incorporated increases with time. One /sup 18/O atom is incorporated rapidly into the carboxyl group of ABA, whereas the other two atoms are very slowly incorporated into the ring oxygens. The fourth oxygen atom in the carboxyl group of ABA is derived from water. ABA from stressed roots of Xanthium incubated in /sup 18/O/sub 2/ shows a labeling pattern similar to that of ABA in stressed leaves, but with incorporation of more /sup 18/O into the tertiary hydroxyl group at C-1' after 6 and 12 hours than found in ABA from stressed leaves. It is proposed that the precursors to stress-induced ABA are xanthophylls, and that a xanthophyll lacking an oxygen function at C-6 plays a crucial role in ABA biosynthesis in Xanthium roots. In turgid Xanthium leaves, /sup 18/O is incorporated into ABA to a much lesser extent that it is in stressed leaves, whereas exogenously applied /sup 14/C-ABA is completely catabolized within 48 hours. This suggests that ABA in turgid leaves is either (a) made via a biosynthetic pathway which is different from the one in stressed leaves, or (b) has a half-life on the order of days as compared with a half-life of 15.5 hours in water-stressed Xanthium leaves. Phaseic acid showed a labeling pattern similar to that of ABA, but with an additional /sup 18/O incorporated during 8'-hydroxylation of ABA to phaseic acid.

• Research Organization: Michigan State Univ., East Lansing
• DOE Contract Number: AC02-76ER01338
• OSTI ID: 5403238
• Journal Information: Plant Physiol.; (United States), Journal Name: Plant Physiol.; (United States) Vol. 85:3; ISSN PLPHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ABSCISIC ACID
AUXINS
BIOLOGICAL HALF-LIFE
BIOLOGICAL PATHWAYS
BIOLOGICAL STRESS
BIOSYNTHESIS
CARBON 14 COMPOUNDS
CARBOXYLIC ACIDS
EVEN-EVEN NUCLEI
ISOTOPE APPLICATIONS
ISOTOPES
LABELLED COMPOUNDS
LEAVES
LIGHT NUCLEI
MONOCARBOXYLIC ACIDS
NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXYGEN 18
OXYGEN ISOTOPES
PLANT GROWTH REGULATORS
PLANTS
ROOTS
STABLE ISOTOPES
SYNTHESIS
TRACER TECHNIQUES