Functional analysis of shikimate pathway gene duplicates

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This application focuses on the functional annotation of shikimate pathway gene duplicates in plants and microbes. Specifically, we will investigate the function of plant shikimate kinase and microbial shikimate dehydrogenase gene duplicates. We have identified two shikimate kinase gene duplicates in plants, which we annotated as SKL1 and SKL2. The encoded proteins do not have shikimate kinase activity, but have evolved novel biological functions in plants. SKL1 has evolved a function in plastid development and SKL2 confers salinity tolerance during seed germination. We will investigate the biochemical reaction catalyzed by these proteins in light of their respective biological function. SKL1 is an excellent target for the development of novel herbicides in crops because we have shown that it is absolutely required for plant growth. Similarly, progress on SKL2 will enhance our understanding of the mechanism of salinity tolerance in crop plants. The second aspect of this proposal deals with microbial shikimate dehydrogenases. We identified five distinct functional groups of shikimate dehydrogenses in microbes, AroE, YdiB, SDHL, Rif1, and Ael1. These shikimate dehydrogenase gene duplicates participate in diverse biochemical activities. Interestingly, all five classes are found only in some soil borne organisms, including Pseudomonas putida. The genes for some of these proteins are found in genetic clusters, called operons. These operons may represent metabolic pathways for the breakdown of aromatic compounds. As such findings from our studies may have direct implications on bioremediation processes especially for areas where these aromatic compounds are found in elevated levels.