DEFECTIVE SYNTHESIS OF PORPHYRINS IN BARLEY PLASTIDS CAUSED BY MUTATION IN NUCLEAR GENES
DEFECTIVE SYNTHESIS OF PORPHYRINS IN BARLEY PLASTIDS CAUSED BY MUTATION IN NUCLEAR GENES
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DOI：
10.1016/0304-4165(72)90086-4
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发表时间：
1972-01-01
期刊：
影响因子：
--
通讯作者：
GOUGH, S
中科院分区：
文献类型：
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作者：
GOUGH, S
在黑暗中用δ-氨基乙酰丙酸喂养大麦中某些致死叶绿素突变体的幼苗时，积累原叶绿素的前体。通过薄层色谱法和光谱法鉴定了这些突变体及其野生型中积累的卟啉。突变体在threexanthaloci和onealbinalocus积累主要是原卟啉。本文提出了一种利用光谱回归分析定量测定混合物中卟啉的新方法，即用δ-氨基乙酰丙酸盐处理的黄嘌呤突变体，其地上部积累的卟啉总量与野生型相同，而用δ-氨基乙酰丙酸盐处理的黄嘌呤突变体，其地上部积累的卟啉总量与野生型相同。野生型产生的卟啉中约90%是原叶绿素，其余为原卟啉。在thexan-f、xan-g、xan-handalb-eloci的突变体中，总积累的卟啉的80-97%是原卟啉，3-20%是原叶绿素。mucanxan-u21以尿卟啉的形式产生总卟啉的35%，而xan-l35以镁原卟啉的形式积累48%。没有一个突变体被δ-氨基乙酰丙酸完全阻断了原叶绿素的合成，因此认为大麦核基因组中的突变阻断了原卟啉和原叶绿素的合成。在原卟啉单甲酯镁之后，mucluxan-l35具有代谢阻断，而多效性更强的mucluxan-u21在尿卟啉和原卟啉之间的途径中包含主要损伤。后一种突变体也缺乏原卟啉转化为原叶绿素以及类胡萝卜素的合成。除了卟啉和类胡萝卜素合成的一般减少外，alb-e 16在将原卟啉转化为原叶绿素的过程中具有特定的阻断作用。在光合生物中积累叶绿素前体的突变体的比较研究的基础上，提出藻类和种子植物的叶绿素合成酶在叶绿体中至少占据两个区室：一种含有将δ-氨基乙酰丙酸转化为原卟啉的酶，另一种由原卟啉形成原叶绿素。突变体提供的证据表明，在种子植物中，叶绿素合成的每一个中间体都可以调节δ-氨基乙酰丙酸的形成，而在藻类中，只有原叶绿素和叶绿素可以归因于这样的功能。
Seedlings of certain lethal chlorophyll mutants in barley accumulate precursors of protochlorophyllide upon feeding with δ-aminolevulinate in the dark. The porphyrins accumulated in these mutant shoots and their wild types have been identified by thin-layer chromatography and spectroscopy. Mutants at threexanthaloci and onealbinalocus accumulate mainly protoporphyrin. Mutants at two otherxanthaloci accumulate, in addition to protoporphyrin, uroporphyrin or magnetism protoporphyrin and its monomethyl ester, respectively.A new method for the quantitative determination of porphyrins in mixtures, utilising regression analysis of the spectra, is described.The total amount of porphyrins accumulated by the shoots of any one of thexanthamutants fed δ-aminolevulinate is the same as the wild type; thealbinamutant accumulates less. About 90% of the porphyrin produced in the wild type is protochlorophyllide and the rest protoporphyrin. In mutants at thexan-f, xan-g, xan-handalb-eloci, 80–97% of the total accumulated porphyrins is protoporphyrin and 3–20% protochlorophyllide. The mutantxan-u21produces 35% of the total prophyrins as uroporphyrin, whereasxan-l35accumulates 48% as magnesium protoporphyrins. None of the mutants is absolutely blocked in protochlorophyllide synthesis when fed δ-aminolevulinate.It is concluded that mutations in the nuclear genesxan-f, -gand-hof barley block the early steps between protoporphyrin and protochlorophyllide. The mutantxan-l35has a metabolic block after magnesium protoporphyrin monomethyl ester, whereas the more pleiotropic mutantxan-u21contains a major lesion in the pathway between uroporphyrin and protoporphyrin. The latter mutant is also deficient in the conversion of protoporphyrin to protochlorophyllide as well as in carotenoid synthesis. Besides a general reduction in porphyrin and carotenoid synthesis,alb-e16has a specific block in the conversion of protoporphyrin to protochlorophyllide.On the basis of a comparative survey of mutants accumulating chlorophyll precursors in photosynthetic organisms, it is suggested that the chlorophyll-synthesising enzymes of algae and seed-plants occupy at least two compartments in the chloroplast: one containing the enzymes converting δ-aminolevulinate to protoporphyrin and the other forming protochlorophyllide from protoporphyrin. The mutants provide evidence that in seed-plants every intermediate in chlorophyll synthesis can regulate the formation of δ-aminolevulinate, whereas in algae only protochlorophyllide and chlorophyll can be ascribed such a function.