Fritz Christina, Palacios-Rojas Natalia, Feil Regina, Stitt Mark
Department 2, Max Planck Institute for Molecular Plant Physiology, Am Muehlenberg 1, D-14476 Golm, Germany.
Plant J. 2006 May;46(4):533-48. doi: 10.1111/j.1365-313X.2006.02715.x.
Interactions between nitrogen and carbon metabolism modulate many aspects of the metabolism, physiology and development of plants. This paper investigates the contribution of nitrate and nitrogen metabolism to the regulation of phenylpropanoid and nicotine synthesis. Wild-type tobacco was grown on 12 or 0.2 mm nitrate and compared with a nitrate reductase-deficient mutant [Nia30(145)] growing on 12 mm nitrate. Nitrate-deficient wild-type plants accumulate high levels of a range of phenylpropanoids including chlorogenic acid, contain high levels of rutin, are highly lignified, but contain less nicotine than nitrogen-replete wild-type tobacco. Nia30(145) resembles nitrate-deficient wild-type plants with respect to the levels of amino acids, but accumulates large amounts of nitrate. The levels of phenylpropanoids, rutin and lignin resemble those in nitrogen-replete wild-type plants, whereas the level of nicotine resembles that in nitrate-deficient wild-type plants. Expression arrays and real time RT-PCR revealed that a set of genes required for phenylpropanoid metabolism including PAL, 4CL and HQT are induced in nitrogen-deficient wild-type plants but not in Nia30(145). It is concluded that nitrogen deficiency leads to a marked shift from the nitrogen-containing alkaloid nicotine to carbon-rich phenylpropanoids. The stimulation of phenylpropanoid metabolism is triggered by changes of nitrate, rather than downstream nitrogen metabolites, and is mediated by induction of a set of enzymes in the early steps of the phenylpropanoid biosynthetic pathway.
氮代谢与碳代谢之间的相互作用调节着植物代谢、生理及发育的诸多方面。本文研究了硝酸盐和氮代谢对苯丙烷类化合物和尼古丁合成调控的贡献。将野生型烟草种植在12 mM或0.2 mM硝酸盐环境中，并与在12 mM硝酸盐环境中生长的硝酸盐还原酶缺陷型突变体[Nia30(145)]进行比较。硝酸盐缺乏的野生型植物积累了高水平的一系列苯丙烷类化合物，包括绿原酸，含有高水平的芦丁，高度木质化，但尼古丁含量低于氮充足的野生型烟草。Nia30(145)在氨基酸水平上类似于硝酸盐缺乏的野生型植物，但积累了大量硝酸盐。苯丙烷类化合物、芦丁和木质素的水平类似于氮充足的野生型植物，而尼古丁水平类似于硝酸盐缺乏的野生型植物。表达阵列和实时RT-PCR显示，在氮缺乏的野生型植物中，一组苯丙烷类代谢所需的基因，包括PAL、4CL和HQT被诱导，但在Nia30(145)中未被诱导。得出的结论是，氮缺乏导致从含氮生物碱尼古丁向富含碳的苯丙烷类化合物的显著转变。苯丙烷类代谢的刺激是由硝酸盐的变化触发的，而不是下游的氮代谢产物，并且是由苯丙烷类生物合成途径早期步骤中一组酶的诱导介导的。
