Class-1 hemoglobins, nitrate and NO levels in anoxic maize cell-suspension cultures
Class-1 hemoglobins, nitrate and NO levels in anoxic maize cell-suspension cultures
复制标题
DOI：
10.1007/s00425-004-1212-y
复制
发表时间：
2004-05-01
期刊：
影响因子：
4.3
通讯作者：
Hill, RD
中科院分区：
文献类型：
--
作者：
Dordas, C;Hasinoff, BB;Hill, RD
一氧化氮(NO)是一种活性气体，参与了动植物和微生物的多种生物过程。前人的工作已经证明，在低氧条件下，紫花苜蓿(Medicago sativa L.)检测到的NO水平与组织中表达的1类血红蛋白的表达水平呈负相关。本研究的目的是：检测转基因玉米(Zea Mays L.)是否产生NO。细胞悬浮培养暴露在缺氧生长条件下；确定1类血红蛋白与在这些条件下检测到的一氧化氮的量之间是否存在类似的关系；以及估计组织中一氧化氮的形成和分解的途径。玉米细胞悬浮培养，转化为表达大麦血红蛋白正义或反义链，用于高表达或低表达1类血红蛋白。以空载体转化的玉米细胞悬浮培养为对照。在低氧压下处理24 h的玉米细胞中检测到高达500nmoL的NO(GFW)(-1)。不同细胞系在缺氧条件下的稳态NO水平与细胞内的血红蛋白水平呈负相关。在好氧生长条件下没有检测到NO的产生。光谱数据表明，重组玉米血红蛋白与NO反应生成高铁血红蛋白和硝酸根。用(NO3-)-N-15和电子顺磁共振波谱分析表明，在缺氧的玉米细胞悬浮培养中，硝酸盐是NO的前体，这表明在缺氧过程中，NO是通过硝酸还原酶生成的。这些结果表明，在低氧压下生长的植物组织中产生了NO，这表明1类血红蛋白在调节NO水平方面具有重要功能。
Nitric oxide (NO) is a reactive gas involved in many biological processes of animals, plants and microbes. Previous work has demonstrated that NO is formed during hypoxia in alfalfa (Medicago sativa L.) root cultures and that the levels of NO detected are inversely related to the levels of expression of class-1 hemoglobin expressed in the tissue. The objectives of this study were: to examine whether NO is produced in transgenic maize (Zea mays L.) cell-suspension cultures exposed to anoxic growth conditions; to determine whether a similar relationship existed between a class-1 hemoglobin and the amount of NO detected under these conditions; and, to estimate the route of formation and breakdown of NO in the tissue. Maize cell-suspension cultures, transformed to express the sense or antisense strands of barley hemoglobin were used to overexpress or underexpress class-1 hemoglobin. A maize cell-suspension culture transformed with an empty vector was used as a control. Up to 500 nmol NO (g FW)(-1) was detected in maize cells exposed to low oxygen tensions for 24 h. The steady-state levels of NO in the different cell lines under anoxic conditions had an inverse relationship to the level of hemoglobin in the cells. There was no detectable NO produced under aerobic growth conditions. Spectroscopic data demonstrated that recombinant maize hemoglobin reacted with NO to form methemoglobin and NO3-. Nitrate was shown to be a precursor of NO in anoxic maize cell-suspension cultures by using (NO3-)-N-15 and electron paramagnetic resonance spectroscopy, suggesting that NO is formed via nitrate reductase during hypoxia. The results demonstrate that NO is produced in plant tissues grown under low oxygen tensions and suggest that class-1 hemoglobins have a significant function in regulating NO levels.