Investigating the Regulation of Nod Factor Production in Burkholderia tuberum
Mentor:Dr. Michelle Lum, Associate Professor of Biology, Loyola Marymount University
Hassan Abdulla, Loyola Marymount University Dr. Michelle Lum, Loyola Marymount University Nitrogen is one of the required nutrients for plant growth, but it is not always readily available for use by plants. Nitrogen fixation is necessary to convert molecular nitrogen (N2) into a form usable by plants, ammonia. As part of a symbiotic relationship with plants, various rhizobia trigger changes within a plant’s roots, creating nodules, in a process known as nodulation. Until recently, it was thought that only alpha-proteobacteria nodulate plants. Now, members of beta-proteobacteria have been observed engaging in nodulation. Although the nodulation itself of beta-proteobacteria appears functionally similar to that of alpha-proteobacteria, little is known about the mechanism by which the beta-proteobacteria regulate nodulation. We are interested specifically in the methods by which Burkholderia tuberum, a beta-proteobacteria, regulates the nodulation process. We hypothesize that B. tuberum regulates nodulation in a manner similar to alpha-proteobacteria. In alpha-rhizobia, the nod genes are expressed in response to flavonoids, a group of plant compounds released from the roots. The gene expression causes the production of signaling molecules called Nod factors, which begin the process of nodulation. To investigate Nod factor regulation, we are making nod gene promoter fusions to the lacZ reporter gene, which will allow us to monitor promoter activity. We amplified the nodA and nodC promoters via the polymerase chain reaction. Restriction enzymes were used to digest the PCR products so that they could be cloned into the PVIK112 vector that contains the lacZ gene. We have almost completed construction of the vectors. Tswill, and lacZ activity measured to monitor promoter activity in response to potential inducers such as plant exudates and flavonoids. Our results will shed light on how conserved the nodulation pathways are between alpha and beta-rhizobia.