METABOLIC COSTS OF TERPENOID ACCUMULATION IN HIGHER-PLANTS
METABOLIC COSTS OF TERPENOID ACCUMULATION IN HIGHER-PLANTS
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DOI：
10.1007/bf02059810
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发表时间：
1994-06-01
影响因子：
2.3
通讯作者：
GERSHENZON, J
中科院分区：
文献类型：
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作者：
GERSHENZON, J
任何植物性状的净值都可以通过衡量与该性状相关的成本和收益来评估。在这一问题的其他贡献者研究了萜类化合物对植物可能的益处的同时，本文根据萜类生物化学的最新进展，探讨了萜类化合物在植物中积累的代谢成本。由于其广泛的化学还原作用，每克萜类化合物的制造成本高于大多数其他初级和次级代谢物，而由于萜类生物合成酶显然不与其他代谢途径共享，因此制造萜类化合物的酶成本也很高。事实上，植物细胞甚至可能拥有不止一组酶，用于催化萜类化合物形成的基本步骤。萜类化合物通常被隔离在复杂的多细胞分泌结构中，因此这些物质的储存成本也可能很高。然而，并不是所有涉及萜类积累的过程都需要投入大量的资源。例如，由于没有证据表明大量的萜类化合物由于代谢周转、挥发或淋溶而损失，因此维持萜类化合物池的成本可能不高。此外，植物可能会通过使用单独的化合物来发挥多种作用，或者通过分解不再需要的物质来降低它们的净萜类成本，尽管目前尚不清楚这种做法是否普遍存在。这些发现(以及萜类生物化学和生理学的其他方面)与当前几种植物防御理论的假设和预测有关，包括碳营养平衡假说、生长分化平衡假说和资源可获得性假说。
The net value of any plant trait can be assessed by measuring the costs and benefits associated with that trait. While the other contributors to this issue examine the possible benefits of terpenoids to plants, this article explores the metabolic costs of terpenoid accumulation in plants in the light of recent advances in terpenoid biochemistry. Terpenoids are more expensive to manufacture per gram than most other primary and secondary metabolites due to their extensive chemical reduction, The enzyme costs of making terpenoids are also high since terpenoid biosynthetic enzymes are apparently not shared with other metabolic pathways. In fact, plant cells may even possess mom than one set of enzymes for catalyzing the basic steps of terpenoid formation. Terpenoids are usually sequestered in complex, multicellular secretory structures, and so storage costs for these substances are also likely to be substantial. However, not all of the processes involved in terpenoid accumulation require large investments of resources. For instance, the maintenance of terpenoid pools is probably inexpensive because there is no evidence that substantial quantities of terpenes are lost as a result of metabolic turnover, volatilization, or leaching. Moreover, plants may reduce their net terpenoid costs by employing individual compounds in more than one role or by catabolizing substances that are no longer needed, although it is still unclear if such practices are widespread. These findings (and other facets of terpenoid biochemistry and physiology) are discussed in relation to the assumptions and predictions of several current theories of plant defense, including the carbon-nutrient balance hypothesis, the growth-differentiation balance hypothesis, and the resource availability hypothesis.