Nitrogen metabolism is important for physiological processes during normal growth and development, as well as plant defence responses. Second‐stage juveniles of the cyst nematode Heterodera schachtii penetrate into the root and initiate permanent feeding sites called syncytia, from which they draw all necessary nutrients. To unravel whether the cyst nematode infestation changes nitrogen metabolism, the enzymatic activity and gene expression of nitrate (NIA) and nitrite (NIR) reductases and glutamate dehydrogenase (GDH), as well as levels of the metabolites nitrates, nitrites, and ammonium ions were estimated both locally in inoculated roots and systemically in shoots of inoculated Arabidopsis thaliana plants at 3, 7, and 15 days post‐inoculation (dpi). Moreover, gene expression of long hypocotyle 5 (HY5), a basic‐region leucine zipper (bZIP) transcription factor, was also determined, to learn more about the potential transcriptional regulation of the analysed enzymes. It was shown that the activity of nitrogen‐related enzymes and the content of metabolites fluctuated during the whole period of infection. These results were accompanied by organ‐specific and dpi‐dependent gene expression patterns. The high gene expression level of HY5 in infected roots at 7 and 15 dpi coexisted with enhanced expression of NIA1 and NIR1 at 7 dpi and NIA2 at 15 dpi. Enhanced HY5 expression level in shoots of infected plants at 15 dpi was followed by up‐regulation of NIA1 expression, suggesting that HY5 may regulate the gene expression of NIA and NIR during nematode infection. Our results indicate that changes in plant nitrogen metabolism occur during cyst nematode infection.

中文翻译：

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Schachtii杂种感染影响拟南芥的氮代谢

氮代谢对于正常生长和发育期间的生理过程以及植物防御反应非常重要。schachtii线虫的第二阶段幼虫渗透到根部并启动称为合胞体的永久性摄食位点，从中吸取所有必需的养分。为了揭示囊肿线虫是否改变了氮代谢，硝酸盐（NIA）和亚硝酸盐（NIR）还原酶和谷氨酸脱氢酶（GDH）的酶活性和基因表达，以及硝酸盐，亚硝酸盐和铵离子的代谢水平估计在接种的根中和在拟南芥的芽中系统地估计接种后第3、7和15天（dpi）种植。此外，还确定了长次叶5（HY5）（一种基本区域亮氨酸拉链（bZIP）转录因子）的基因表达，以了解有关所分析酶的潜在转录调控的更多信息。结果表明，在整个感染过程中，氮相关酶的活性和代谢产物的含量均发生波动。这些结果伴随着器官特异性和dpi依赖的基因表达模式。高基因表达水平HY5在感染根在与增强表达并存7和15 dpi的NiAl的和NIR1在7 dpi和NIA2在15 dpi的。增强型HY5在15 DPI受感染的植物的芽表达水平，随后的上调NiAl的表达，提示HY5可调节的基因表达的NIA和NIR线虫感染期间。我们的结果表明，植物氮代谢的变化发生在囊肿线虫感染期间。