PLANT PHYSIOLOGY , Vol 110, Issue 1 179-186, Copyright © 1996 by American Society of Plant Biologists
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BIOCHEMISTRY AND ENZYMOLOGY |
Biochemistry of Short-Chain Alkanes (Tissue-Specific Biosynthesis of n-Heptane in Pinus jeffreyi)
T. J. Savage, B. S. Hamilton and R. Croteau
Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164-6340 (T.J.S.,R.C.)
Short-chain (C7-C11) alkanes accumulate as the volatile component of
oleoresin (pitch) in several pine species native to western North America.
To establish the tissue most amenable for use in detailed studies of
short-chain alkane biosynthesis, we examined the tissue specificity of
alkane accumulation and biosynthesis in Pinus jeffreyi Grev. & Balf.
Short-chain alkane accumulation was highly tissue specific in both
2-year-old saplings and mature trees; heart-wood xylem accumulated alkanes
up to 7.1 mg g-1 dry weight, whereas needles and other young green tissue
contained oleoresin with monoterpenoid, rather than paraffinic, volatiles.
These tissue-specific differences in oleoresin composition appear to be a
result of tissue-specific rates of alkane and monoterpene biosynthesis;
incubation of xylem tissue with [14C]sucrose resulted in accumulation of
radiolabel in alkanes but not monoterpenes, whereas incubation of foliar
tissue with 14CO2 resulted in the accumulation of radiolabel in
monoterpenes but not alkanes. Furthermore, incubation of xylem sections
with [14C]acetate resulted in incorporation of radiolabel into alkanes at
rates up to 1.7 nmol h-1 g-1 fresh weight, a rate that exceeds most
biosynthetic rates reported with other plant systems for the incorporation
of this basic precursor into natural products. This suggests that P.
jeffreyi may provide a suitable model for elucidating the enzymology and
molecular biology of short-chain alkane biosynthesis.
