Effects of genetic modification of nitrate reductase expression on 15NO3- uptake and reduction in Nicotiana plants
Effects of genetic modification of nitrate reductase expression on 15NO3- uptake and reduction in Nicotiana plants
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DOI：
10.1046/j.1365-3040.1998.00269.x
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发表时间：
1998-01-01
影响因子：
7.3
通讯作者：
Rufty, TW
中科院分区：
文献类型：
--
作者：
Gojon, A;Dapoigny, L;Rufty, TW
以烟草（Nicotiana tabacum）和白花烟草（Nicotiana plumbaginifolia）的9个转化体为材料，研究了硝酸还原酶（NR）低表达和过表达对植物NO3-利用的生理影响。低NR和高NR转化体的根和叶中的离体NR活性（NRA）分别为野生型植株中所测量的那些的5-10%和150- 200%。NR表达水平显著影响离体叶片和完整植株中的NO_3还原效率。O-15（3）-还原量在低NR植株中占（NO3-）-N-15吸收量的15-45%，在野生型中占40-80%，在高NR植株中高达95%。然而，在高NR基因型中，总（NO3-）-N-15同化量与温和型植株相比没有显著增加，由于（NO3-）-N-15还原效率的提高被根系对（NO3-）-N-15吸收的降低所抵消，因此NO3-吸收的抑制可能是NO3-内流负反馈调节的结果，并被解释为NO3-吸收的调节，以防止过量的氨基酸合成。在NR低表达基因型中，与野生型相比，低的（NO3-）-N-15还原效率通常也与净（NO3-）-N-15吸收的减少有关。因此，NR的低表达导致在植物中的N-15合成减少的抑制，虽然效果比从非常低的NR的预期要不那么明显。低氮植物对NO3-吸收的限制强调了NO3-同化产物不是NO3-吸收系统下调的唯一因素。
The physiological consequences for NO3- utilization by the plant of underexpression and overexpression of nitrate reductase (NR) were investigated in nine transformants of Nicotiana tabacum and Nicotiana plumbaginifolia. The irt vitro NR activities (NRA) in both roots and leaves of low- and high-NR tobacco transformants ranged from 5-10% to 150-200%, respectively, of those measured in wild-type plants, The level of NR expression markedly affected the NO3- reduction efficiency in detached leaves and intact plants, In both species, O-15(3)- reduction ranged from 15-45% of (NO3-)-N-15 uptake in the low-NR plants, to 40-80% in the wild-type, and up to 95% in high-NR plants, In the high-NR genotypes, however, total (NO3-)-N-15, assimilation was not significantly increased when compared with that in mild-type plants, because the higher (NO3-)-N-15 reduction efficiency was offset by lower (NO3-)-N-15 uptake by the roots, The inhibition of NO3- uptake appeared to be the result of negative feedback regulation of NO3- influx, and is interpreted as an adjustment of NO3- uptake to prevent excessive amino acid synthesis, In genotypes underexpressing NR, the low (NO3-)-N-15 reduction efficiency also was generally associated with a decrease in net (NO3-)-N-15 uptake as compared with the wild type. Thus, underexpression of NR resulted in an inhibition of reduced N-15 synthesis in the plant, although the effect was much less pronounced than that expected from the very low NRAs. The restricted NO3- uptake in low-NR plants emphasizes the point that the products of NO3- assimilation are not the only factors responsible for down-regulation of the NO3- uptake system.