La Rocca N, Rascio N, Oster U, Rüdiger W
Dipartimento di Biologia, Universitá degli Studi di Padova, Italy.
Planta. 2001 May;213(1):101-8. doi: 10.1007/s004250000477.
The effect of amitrole, known as an inhibitor of carotenoid biosynthesis, upon tetrapyrrole biosynthesis and its regulation has been studied. Etiolated barley (Hordeum vulgare L.) seedlings, grown in 125 microM amitrole, accumulated high levels of 5-aminolevulinate, Mg-protoporphyrin, Mg-protoporphyrin monomethyl ester, and protochlorophyllide. The amitrole-treated seedlings did not form paracrystalline prolamellar bodies, and the induction of Lhc and RbcS gene expression was reduced by non-photooxidative, low-intensity light. None of these events was observed upon treatment of the seedlings with 100 microM norflurazon, another inhibitor of carotenoid biosynthesis. The effect of amitrole cannot be explained solely by interaction with a presumed feedback inhibition of 5-aminolevulinate synthesis since incubation with amitrole and 5-aminolevulinate indicated that deregulation also occurs at later steps of tetrapyrrole biosynthesis. A possible relationship between this deregulation and ultrastructural changes is discussed. In connection with previously published data, we discuss Mg-protoporphyrin and its monomethyl ester as possible candidates for a "plastid signal" that operates as a negative factor, reducing the expression of Lhc and RbcS genes in this higher plant.
已对作为类胡萝卜素生物合成抑制剂的杀草强对四吡咯生物合成及其调控的影响进行了研究。在含有125微摩尔杀草强的条件下生长的黄化大麦（Hordeum vulgare L.）幼苗积累了高水平的5-氨基乙酰丙酸、镁原卟啉、镁原卟啉单甲酯和原叶绿素酸酯。经杀草强处理的幼苗未形成副晶质的原片层体，并且在非光氧化的低强度光照下，Lhc和RbcS基因表达的诱导受到了抑制。在用100微摩尔去甲氟草酮（另一种类胡萝卜素生物合成抑制剂）处理幼苗时，未观察到上述任何现象。杀草强的作用不能仅通过与假定的5-氨基乙酰丙酸合成反馈抑制的相互作用来解释，因为用杀草强和5-氨基乙酰丙酸一起孵育表明，在四吡咯生物合成的后期步骤也会发生失调。讨论了这种失调与超微结构变化之间的可能关系。结合先前发表的数据，我们讨论了镁原卟啉及其单甲酯作为“质体信号”的可能候选物，该信号作为一种负因子，降低了这种高等植物中Lhc和RbcS基因的表达。
