Department of Biology, Lund University, Biology building, Sölvegatan 35, SE-223 62 Lund, Sweden.
Mol Plant. 2014 Feb;7(2):356-68. doi: 10.1093/mp/sst115. Epub 2013 Aug 12.
Ca(2+)-dependent oxidation of cytosolic NADPH is mediated by NDB1, which is an external type II NADPH dehydrogenase in the plant mitochondrial electron transport chain. Using RNA interference, the NDB1 transcript was suppressed by 80% in Arabidopsis thaliana plants, and external Ca(2+)-dependent NADPH dehydrogenase activity became undetectable in isolated mitochondria. This was linked to a decreased level of NADP(+) in rosettes of the transgenic lines. Sterile-grown transgenic seedlings displayed decreased growth specifically on glucose, and respiratory metabolism of (14)C-glucose was increased. On soil, NDB1-suppressing plants had a decreased vegetative biomass, but leaf maximum quantum efficiency of photosystem II and CO2 assimilation rates, as well as total respiration, were similar to the wild-type. The in vivo alternative oxidase activity and capacity were also similar in all genotypes. Metabolic profiling revealed decreased levels of sugars, citric acid cycle intermediates, and amino acids in the transgenic lines. The NDB1-suppression induced transcriptomic changes associated with protein synthesis and glucosinolate and jasmonate metabolism. The transcriptomic changes also overlapped with changes observed in a mutant lacking ABAINSENSITIVE4 and in A. thaliana overexpressing stress tolerance genes from rice. The results thus indicate that A. thaliana NDB1 modulates NADP(H) reduction levels, which in turn affect central metabolism and growth, and interact with defense signaling.
依赖 Ca(2+)的细胞质 NADPH 氧化由 NDB1 介导，NDB1 是植物线粒体电子传递链中外源 II 型 NADPH 脱氢酶。通过 RNA 干扰，NDB1 转录本在拟南芥植物中被抑制了 80%，分离的线粒体中也检测不到外部 Ca(2+)-依赖性 NADPH 脱氢酶活性。这与转基因系中 NADP(+)水平降低有关。无菌生长的转基因幼苗在葡萄糖上的生长受到特异性抑制，（14)C-葡萄糖的呼吸代谢增加。在土壤中，NDB1 抑制植物的营养生物量减少，但叶片最大光化学效率和 CO2 同化率以及总呼吸率与野生型相似。体内替代氧化酶活性和能力在所有基因型中也相似。代谢组学分析显示，转基因系中的糖、柠檬酸循环中间产物和氨基酸水平降低。NDB1 抑制诱导了与蛋白质合成以及硫代葡萄糖苷和茉莉酸代谢相关的转录组变化。转录组变化也与缺乏 ABAINSENSITIVE4 的突变体和拟南芥中过量表达来自水稻的胁迫耐受基因的变化重叠。因此，结果表明，拟南芥 NDB1 调节 NADP(H)还原水平，进而影响中心代谢和生长，并与防御信号相互作用。
