CAREER: Identification and Characterization of Phosphate- Starvation Inducible Genes in Rhizobium meliloti

9420798 McDermott研究计划：文献中包含了大量的例子，这些例子表明豆科植物-根瘤菌共生体很容易对磷（P）肥料的施用做出反应，并且与非豆科植物相比，豆科植物的最佳生长需要更高的P。 这种具有重要农艺学意义的植物-微生物相互作用的各种共生特征被磷肥显著增强。 然而，我们对共生固氮的磷需求增加的基础，或P反应的基础，特别是类细菌在这种反应中的作用知之甚少。 在提出的工作中，R.苜蓿将用于开始对受磷有效性影响的根瘤菌基因进行定性和定量评估。 R.苜蓿属菌株104 A14已经用携带无启动子的lacZ基因的转座子突变，当插入相对于活性启动子处于正确方向时，lacZ基因表现为报告基因。 在广泛筛选后，鉴定了19种突变体，其在细胞受到P-应激时相对于当细胞被提供适当的P时表现出显著更大的报道基因活性。将进一步表征报道突变体以确定它们在P获得中具有什么作用（如果有的话），野生型基因可能具有什么代谢作用，以及它们的表达是否受到其他环境刺激的影响。 此外，它们的共生表型将与P-利用效率或效率低下的宿主基因型一起确定，并且在P对于宿主植物是限制性的或过量的条件下确定。 最后，将在序列水平上研究选定的突变体。 将对受影响的基因进行克隆和测序，以帮助鉴定。 教育计划：教育计划包括三个层次的教学：1）新课程的开发，2）传统的研究生和博士后科学家培训，3）专业本科生研究培训。 正在开发的新课程包括一门本科课程和一门研究生课程，隔年授课。 一个专门的本科研究培训计划也被描述。 该计划的目的是识别有才华的本科生，并为他们提供一对一的培训。 该计划旨在为那些计划攻读研究生和从事研究型职业的学生提供培训机会。 这些本科生进行的研究将在PI的直接监督下进行，并将成为研究计划中描述的工作的一部分。

9420798 McDermott Research Plan: The literature contains numerous examples that shows the legume-Rhizobium symbiosis readily responds to the application of phosphorus (P) fertilizer, and that nodulated legumes have a higher P requirement for optimum growth than non-nodulated legumes. Various symbiotic features of this agronomically important plant-microbe interaction are significantly enhanced by P fertilization. However, we know little about the basis for increased P requirements of symbiotic nitrogen fixation, or the basis of the P respone, particularly the role of the bacterioids in this response. In the proposed work, R. meliloti will be used to begin a qualitative and quantitative assessment of Rhizobium genes that are affected by P availability. R. meliloti, strain 104A14, has been mutated with a transposon that carries a promoterless lacZ gene which behaves as a reporter gene when insertion is in the correct orientation relative to the active promoter. After extensive screening, 19 mutants were identified that exhibited significantly greater reporter gene activity when the cells were P-stressed relative to when the cells were provided adeuate P. The reporter mutants will be further characterized to determine what role, if any, they have in P acquisition, what metabolic role the wild-type gene may have, and if their expression is influenced by other environmental stimuli. Further, their symbiosis phenotype will be determined with host genotypes that are either P-use efficient or inefficient, and under conditions where P is either limiting or in excess for the host plant. Finally, selected mutants will be studied at the sequence level. The effected gene(s) will be cloned an sequenced to help in their identification. Education Plan: The Education Plan involves three levels of instruction: 1) development of new courses, 2) traditional graduate student and posdoctoral scientist training, and 3) specialized undergraduate research training. The n ew courses being developed include one undergraduate course and one graduate course, taught in alternate years. A specialized undergraudate research training program is also described. The purpose of this program is to identify talented undergraduate students and provide them with one-on- one training. The program is geared to enhance the training opportunities for those students who are planning on postgraduate school and a research-oriented career. The research conducted by these undergraduates will be under the direct supervision of the PI and will part of the work described in the Research Plan.