Metabolism of monoterpenes in cell cultures of common sage (Salvia officinalis). Biochemical rationale for the lack of monoterpene accumulation
1990
Falk, K.L. | Gershenzon, J. | Croteau, R.
Leaves of common sage (Salvia officinalis) accumulate monoterpenes in glandular trichomes at levels exceeding 15 milligrams per gram fresh weight at maturity, whereas sage cells in suspension culture did not accumulate detectable levels of monoterpenes (less than 0.3 nanograms per gram fresh weight) at any stage of the growth cycle, even in the presence of a polystyrene resin trap. Monoterpene biosynthesis from [U-14C]sucrose was also virtually undetectable in this cell culture system. In vitro assay of each of the enzymes required for the sequential conversion of the ubiquitous isoprenoid precursor geranyl pyrophosphate to (+)-camphor (a major monoterpene product of sage) in soluble extracts of the cells revealed the presence of activity sufficient to produce (+)-camphor at a readily detectable level (greater than 0.3 micrograms per gram fresh weight) at the late log phase of growth. Other monoterpene synthetic enzymes were present as well. In vivo measurement of the ability to catabolize (+)-camphor in these cells indicated that degradative capability exceeded biosynthetic capacity by at least 1000-fold. Therefore, the lack of monoterpene accumulation in undifferentiated sage cultures could be attributed to a low level of biosynthetic activity (relative to the intact plant) coupled to a pronounced capacity for monoterpene catabolism.
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