Submitted to: Plant Biology Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 2/28/2003
Publication Date: 7/25/2003
Citation: Nakata, P.A., McConn, M.M. Genetic manipulation of calcium oxalate crystal formation in medicago truncatula. Plant Biology Annual Meeting. 2003.
Technical Abstract: Calcium oxalate crystals are found in rocks, soil, and living organisms ranging from simple microbes to complex animals. Plants invest a considerable amount of resources and energy into the formation of calcium oxalate crystals. A number of roles for crystal formation in plant growth and development have been assigned based on the prevalence of crystals, their spatial distribution, and the variety of crystal shapes. How and why many plants form crystals of calcium oxalate remains largely unknown. To gain insight into the regulatory mechanisms of crystal formation and function we have screened an EMS mutagenized Medicago truncatula population and identified several different classes of calcium oxalate defective (cod) mutants. The cod mutants exhibited alterations in crystal morphology, distribution, and/or amount. Genetic analysis indicated that crystal formation is a complex process involving several loci. As a step toward determining whether crystal formation plays a critical role in plant growth and development, we characterized the growth, oxalate content, and mineral content of the cod5 mutant that lacks the ability to accumulate appreciable amounts of calcium oxalate. Examination of control plants, using light microscopy, revealed the accumulation of prismatic crystals along the vascular strands in all the different plant tissues with the exception of roots, in which no crystals were observed. In contrast, no prismatic crystals were detected in any of the different tissues of the cod5 mutant. Crystals of calcium oxalate were observed in the pods of cod5, but they were of a different morphology. Measurements of the oxalate content in the different tissues confirmed the cod5 crystal phenotype by exhibiting low oxalate levels compared to those of controls. The cod5 pods did contain measurable oxalate levels, but at levels several times lower than controls. Although compromised in its ability to accumulate crystals of calcium oxalate, cod5 exhibited growth, which was similar to that of controls. Moreover, cod5 and controls contained similar amounts of calcium, sodium, and potassium. Thus, calcium oxalate crystal formation does not appear to be essential for plant growth or development in the case of Medicago truncatula. This finding suggests that reducing the oxalate content in plants is feasible. The ability to manipulate the amount and distribution of crystal formation could have a substantial impact on the production and nutritional quality of plant foods.