Submitted to: Plant Cell Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/27/2012
Publication Date: 7/1/2012
Citation: Nakata, P.A. 2012. Engineering calcium oxalate crystal formation in Arabidopsis. Plant Cell Physiology. 53(7):1275-1282.
Interpretive Summary: Calcium oxalate crystal formation in plants has been shown to help the plant tolerate high metal concentrations that may be present in the soil and in defending the plant against herbivores. The ability to control the formation of these crystals in plants could benefit efforts to protect crops against insect damage and heavy metal accumulation. Our ability to control crystal formation has been hindered by our lack of understanding of how these crystals form. A major stumbling block has been our inability to identify the genes that compose the crystal formation pathway. To aid the effort of gene identification, we report here the engineering of Arabidopsis into a calcium oxalate crystal accumulating plant. One of the primary reasons Arabidopsis was developed as a model plant was for the easy identification of pathway genes and the deciphering of biochemical pathways. Thus generation of a crystal forming Arabidopsis plant will expedite our understanding of calcium oxalate crystal formation in plants.
Technical Abstract: Many plants accumulate crystals of calcium oxalate. Just how these crystals form remains unknown. To gain insight into the mechanisms regulating calcium oxalate crystal formation, a crystal engineering approach was initiated utilizing the non-crystal accumulating plant, Arabidopsis. The success of this approach hinged on the ability to genetically transform Arabidopsis into a calcium oxalate crystal accumulating plant. To accomplish this transformation, two oxalic acid biosynthetic genes, obcA and obcB, from the oxalate-secreting phytopathogen, Burkholderia glumae, were inserted into the Arabidopsis genome. The co-expression of these two bacterial genes in Arabidopsis not only conferred the ability to produce measurable amount of oxalate but also to form crystals of calcium oxalate. Biochemical and cellular studies of crystal accumulation in Arabidopsis revealed features that are similar to those observed in the cells of crystal forming plants. Thus, it appears that at least some of the basic components that comprise the calcium oxalate crystal formation machinery are conserved even in non-crystal accumulating plants.