ASGSB 1999 Annual Meeting Abstracts

QUANTITATIVE PCR AND METABOLIC FLUX ANALYSIS: FACTORS AFFECTING LIGNIN COMPOSITION AND CONTENT. A.M. Anterola, C. Rohwer, L.B. Davin, and N.G. Lewis. Institute of Biological Chemistry, Washington State University, Pullman, WA.

Metabolic flux analysis experiments were conducted with loblolly pine (Pinus taeda) to identify the rate-limiting steps affecting both monolignol (p-coumaryl and coniferyl alcohol) content and composition. HPLC-MS analyses of phenylpropanoid pathway pools, quantification of transcripts (through quantitative PCR) and measurement of enzyme activity induction in the overall phenylpropanoid pathway led to the determination that it is under multi-site modulation, involving phenylalanine ammonia lyase, cinnamate-4-hydroxylase and p-coumarate 3-hydroxylase, respectively. Increasing levels of available (exogenously supplied) phenylalanine resulted in differential increase in amounts of p-coumaryl and coniferyl alcohols, changing their ratios over 24 h from ca. 1:8 at 0 mM phenylalanine to ca. 1:1 at 40 mM phenylalanine. These data provide a biochemical explanation to the preferential formation of p-coumaryl alcohol either during early stages of lignification, or when plants are displaced from their vertical alignment at 1 g; the latter triggers formation of p-coumaryl alcohol rich compression wood tissues essential for stem realignment. 

(Supported by NASA: NAG2-1198).

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