|MC NEAR,JR., DAVID|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 1/20/2006
Publication Date: 4/9/2006
Citation: McNear,Jr., D.H., Gann, J.G., Grusak, M.A., Sherrier, D.J. (2006). The role of metals in root nodule formation and function [abstract]. In: Genes to Crops. 3rd International Conference on Legume Genomics and Genetics, April 9-13, 2006 Brisbane, Queensland, Australia. p. 46.
Technical Abstract: Leguminous plants under nitrogen-starved conditions form a symbiotic relationship with soil bacteria (rhizobia), resulting in the development of a specialized plant organ called the nitrogen-fixing root nodule. During nodule development, the bacteria are released into plant cells where they are enveloped in a plasmalemma-derived compartment called the symbiosome membrane. The symbiosome membrane separates the bacteria from the surrounding cytoplasm and serves as the interface for metabolite exchange between the bacteria and plant. Significant progress has been made toward elucidating the biochemical and genetic mechanisms responsible for symbiosome development and function, in both the rhizobia and host plant. Success of the symbiotic plant-rhizobia relationship depends not only on the adequate delivery of ammonia from the rhizobia to the host plant, but also on the adequate delivery of requisite nutrients from the plant to the bacteria. Among the nutrients necessary for proper nodule function are metals such as Mg, Fe, Mn, and Zn, which are essential cofactors in various bacterial enzymes. Little is known about how these metals are delivered to the bacteria, the concentrations required for proper nodule function, or how their supply affects symbiosome development. Furthermore, we still have much to learn about the effect that bacterial metal demand places on the nutritional status of the host plant, and the impact of metal availability on bacterial development. Therefore, our objectives are to assess the role that metals play in symbiosome formation and overall root nodule function. To do so, we are using a Zn hyperaccumulating mutant of the model legume Medicago truncatula (named raz for “requires additional Zn”), in which the process of symbiosome maturation is disrupted, resulting in the formation of an aberrant root nodule. Initial results indicate that Zn accumulates preferentially within the root nodule and that symbiosome formation is perturbed early in development. Future work will determine the effect of Zn on root nodule development, including a detailed analysis of the cellular Zn distribution within mutant and wild type M. truncatula root tissues, as well as the effect of varying Zn concentrations on the growth and development of free-living rhizobia. This work will help define the roles of zinc in the agronomically important process of root nodule formation and will provide significant new insights into the role that metals play in symbiosome formation and overall nodule function.