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To better understand the roles of LsrA protein in nodulation, a series of analyses of nodules using scanning electron microscopy, genetic and biochemical approaches have been carried out. Our analyses suggest that the lsrA1 nodules contain bacteroids in the invasion and establishing zone only. The lsrA gene expression is active early in the invasion zone and activated later than bacA genes. The lost of LsrA protein dramatically reduced the expression of nifA and fixK, and completely blocked the expression of the nifH gene for nitrogenase. LsrA protein functions early in the bacteroid development and it is essential for the development nitrogen fixing bacteroids.

前期的工作中，苜蓿中华根瘤菌Rm1021中90个候选LysR基因已经被定向插入突变，并筛选在自生生长时期、共生生长时期的表型，以期寻找更多在自生状态或共生固氮中有功能的LysR转录因子。1 针对前期鉴定出的共生固氮必需的lsrA基因，我们应用了一系列扫描电子显微镜技术、生物化学、分子遗传学等方法，发现lsrA基因主要在根瘤侵染区开始表达，表达时序也在侵染阶段左右，但晚于bacA基因表达；LsrA蛋白缺失后根瘤固氮区中缺乏具有固氮能力的类菌体，nifA和fixK基因的转录水平降低，nifH基因的转录被完全阻断，因此LsrA蛋白为根瘤发育所必需，是新的根瘤发育信号传导途径成员。2 通过表型筛选我们鉴定了苜蓿中华根瘤菌的oxyR基因，并研究了它的调节特性。oxyR突变后，苜蓿中华根瘤菌对过氧化氢敏感性提高，适应性降低。

A Cultural Baedeker for Chinese Tourists Abroad Global Travel Writing by Yu QiuyuWhen travelling becomes a " culture shock " and an essential part of globalisation .

中国海外游记文化指南--余秋雨的世界苦旅旅行成为一种"文化震荡"及全球化的一个重要组成部分。

Bailing out the auto industry, one of America's last major manufacturers,is essential to our economic recovery.

百灵了汽车业，美国的最后的主要制造商之一，是必不可少的经济复苏。

It is therefore essential to find a balance point between the rights of the intellectual property and the real product.

这就需要在知识产权人的利益和物权人的利益之间寻找一个平衡点。

The other is the miniature ball bearing, essential in the assembling of a missile-guidance system.

另一件是微型滚珠轴承，这是装配导弹的制导系统所必不可少的。

In this paper,the process flow and essential techniques were introduced in details for the production of poached bamboo shoot can.

该文对水煮笋罐头的生产工艺流程和技术要点做了详细地说明。

To improve productivity and cutting accuracy of wood and to modify characteristics of band saw, it is essential that we study vibration characteristics of band saw.

为了提高木材生产率和加工精度，改善带锯机的工作性能，降低生产成本，对带锯机的振动特性进行研究是十分必要的。

As an essential component in modern wireless communication systems,bandpass filter has attracted more and more attention and got many achievements too.

当今无线通信技术的发展对电路的性能要求越来越高、种类越来越多，新的工艺和设计方法也相应层出不穷。

The essential question is which direction will result in the least damage from the barb.

问题的关键是哪个方向将导致损害最少的矛头。

Making comparisons is essential if you would like loans at bargain basement prices.

比较是必不可少的，如果你想贷款，价格便宜的地下室。

I go to school at night.

我是上上学。

Clear Tip Nasal Aspirator: A soft time and gentle suction action makes removing excess mucus easy.

鼻吸明确提示：一个柔软的时间和温柔吸力行动使消除过剩的粘液容易。