López-Lozano Antonio, Gómez-Baena Guadalupe, Muñoz-Marín Maria del Carmen, Rangel Oriol Alberto, Diez Jesús, García-Fernández Jose Manuel
Departamento de Bioquímica y Biología Molecular, Universidad de Córdoba, 14071-Córdoba, Spain.
Gene Expr. 2009;14(5):279-89. doi: 10.3727/105221609788681204.
The expression of five genes involved in nitrogen assimilation in cyanobacteria, namely glnA, glsF, icd, ntcA, and glnB, encoding three key enzymes from that pathway (glutamine synthetase, glutamate synthase, isocitrate dehydrogenase) and two regulatory proteins (NtcA and PII), was studied in this work. Their changes under different conditions were analyzed by quantitative real-time RT-PCR. Nutrient limitation induced clear modifications on the expression of most studied genes: lack of nitrogen provoked an initial increase, followed by a marked decrease; in the cases of phosphorus and iron starvation, a general, stronger expression decrease was observed, particularly striking in the case of iron. Darkness and addition of the photosynthethic inhibitors DCMU and DBMIB also had a strong effect on gene expression. Methionine sulfoximine and azaserine, inhibitors of glutamine synthetase and glutamate synthase, respectively, provoked a sharp increase in icd expression. These results, together with previous studies, suggest that 2-oxoglutarate could be the molecule utilized by Prochlorococcus to sense the C/N balance. Besides, our results confirm the different regulation of nitrogen assimilation in Prochlorococcus with regard to other cyanobacteria.
本研究对蓝藻中参与氮同化的五个基因（即glnA、glsF、icd、ntcA和glnB）的表达进行了研究，这五个基因编码该途径的三种关键酶（谷氨酰胺合成酶、谷氨酸合酶、异柠檬酸脱氢酶）和两种调节蛋白（NtcA和PII）。通过定量实时RT-PCR分析了它们在不同条件下的变化。营养限制对大多数研究基因的表达产生了明显的改变：缺乏氮会引发最初的增加，随后显著下降；在磷和铁饥饿的情况下，观察到普遍更强的表达下降，在铁饥饿的情况下尤为明显。黑暗以及添加光合抑制剂二氯苯基二甲基脲（DCMU）和二溴甲基异噻唑啉酮（DBMIB）也对基因表达有强烈影响。谷氨酰胺合成酶抑制剂甲硫氨酸亚砜亚胺和谷氨酸合酶抑制剂重氮丝氨酸分别引发icd表达的急剧增加。这些结果与先前的研究一起表明，2-氧代戊二酸可能是原绿球藻用来感知碳/氮平衡的分子。此外，我们的结果证实了原绿球藻中氮同化与其他蓝藻相比存在不同的调控。
