The Mina and Everard Goodman Faculty of Life Sciences, Bar Ilan University, Ramat Gan, Israel.
PLoS One. 2010 Dec 6;5(12):e15104. doi: 10.1371/journal.pone.0015104.
Growth, protein amount, and activity levels of metabolic pathways in Trichodesmium are influenced by environmental changes such as elevated pCO(2) and temperature. This study examines changes in the expression of essential metabolic genes in Trichodesmium grown under a matrix of pCO(2) (400 and 900 µatm) and temperature (25 and 31°C). Using RT-qPCR, we studied 21 genes related to four metabolic functional groups: CO(2) concentrating mechanism (bicA1, bicA2, ccmM, ccmK2, ccmK3, ndhF4, ndhD4, ndhL, chpX), energy metabolism (atpB, sod, prx, glcD), nitrogen metabolism (glnA, hetR, nifH), and inorganic carbon fixation and photosynthesis (rbcL, rca, psaB, psaC, psbA). nifH and most photosynthetic genes exhibited relatively high abundance and their expression was influenced by both environmental parameters. A two to three orders of magnitude increase was observed for glnA and hetR only when both pCO(2) and temperature were elevated. CO(2) concentrating mechanism genes were not affected by pCO(2) and temperature and their expression levels were markedly lower than that of the nitrogen metabolism and photosynthetic genes. Many of the CO(2) concentrating mechanism genes were co-expressed throughout the day. Our results demonstrate that in Trichodesmium, CO(2) concentrating mechanism genes are constitutively expressed. Co-expression of genes from different functional groups were frequently observed during the first half of the photoperiod when oxygenic photosynthesis and N(2) fixation take place, pointing at the tight and complex regulation of gene expression in Trichodesmium. Here we provide new data linking environmental changes of pCO(2) and temperature to gene expression in Trichodesmium. Although gene expression indicates an active metabolic pathway, there is often an uncoupling between transcription and enzyme activity, such that transcript level cannot usually be directly extrapolated to metabolic activity.
在二氧化碳（pCO2）升高和温度升高的环境变化下，束毛藻的生长、蛋白质含量和代谢途径的活性水平受到影响。本研究检测了在 pCO2（400 和 900µatm）和温度（25 和 31°C）矩阵下培养的束毛藻中必需代谢基因的表达变化。我们使用 RT-qPCR 研究了与四个代谢功能群相关的 21 个基因：二氧化碳浓缩机制（bicA1、bicA2、ccmM、ccmK2、ccmK3、ndhF4、ndhD4、ndhL、chpX）、能量代谢（atpB、sod、prx、glcD）、氮代谢（glnA、hetR、nifH）和无机碳固定和光合作用（rbcL、rca、psaB、psaC、psbA）。nifH 和大多数光合作用基因的表达丰度相对较高，并且受到两种环境参数的影响。只有当 pCO2 和温度都升高时，glnA 和 hetR 的表达才会增加两个到三个数量级。二氧化碳浓缩机制基因不受 pCO2 和温度的影响，其表达水平明显低于氮代谢和光合作用基因。许多二氧化碳浓缩机制基因在一天中都有共表达。我们的结果表明，在束毛藻中，二氧化碳浓缩机制基因是组成型表达的。不同功能群的基因在光合和固氮发生的光周期前半段经常共表达，这表明束毛藻中基因表达的紧密而复杂的调控。在这里，我们提供了新的数据，将 pCO2 和温度的环境变化与束毛藻中的基因表达联系起来。尽管基因表达表明存在活跃的代谢途径，但转录和酶活性之间经常存在解偶联，因此转录水平通常不能直接外推到代谢活性。
