Submitted to: Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/31/2002
Publication Date: 2/1/2003
Citation: NAKATA, P.A., MCCONN, M.M. INFLUENCE OF THE CALCIUM OXALATE DEFECTIVE 4 (COD4) MUTATION ON THE GROWTH, OXALATE CONTENT, AND CALCIUM CONTENT OF MEDICAGO TRUNCATULA. PLANT SCIENCE. 2003. v. 164. p. 617-621. Interpretive Summary: Our goal in this experiment was to characterize the calcium and oxalate content in all the tissues of a mutant type of a plant called Medicago truncatula during its growth. We looked at these aspects in the plant's leaves, stems, roots and pods during various stages of growth. We were interested in doing this because we noticed that this mutant has more calcium oxalate crystals than regular Medicago plants. We were wondering what influence this might have on the plant and its growth. We were interested in determining whether this influence might prove useful in some way. For example, we had previous evidence that these crystals could help protect the plant against insects. In that respect, we thought that if we could manipulate the calcium levels, we might make the plant resistant against pathogens that could damage or even kill it. Moreover, we know that the more calcium that is locked into the crystals, the less that is available for the nutrition of an individual who eats this plant. Ultimately, we were able to successfully characterize the contents at various stages of growth. That provided us with the very important first step in the process of understanding such characteristics, and then determining what to do to try to manipulate them for the benefit of such edible plants and for the people who eat them.
Technical Abstract: Calcium oxalate crystal formation has been well documented in plants. The pathway(s) and regulatory mechanism(s) of crystal formation and function, however, remain largely unknown. As a step toward expanding our understanding of crystal formation and function, we characterize the oxalate over-accumulating mutant calcium oxalate defective 4 (cod4). Measurements of oxalate content in the different cod4 tissues showed elevated levels in leaves, stems and pods, compared to the corresponding control tissues. Root oxalate content was similar between cod4 and controls. Microscopic examination of the cod4 tissues revealed that all the tissues with elevated oxalate content accumulated druse crystals in addition to the prismatic crystals that are also present in wild type. With the exception of pods, however, the calcium content did not increase in proportion to the increase in oxalate. Thus, more of the tissue calcium was partitioned into the crystalline form in the leaves and stems from cod4 than controls. Biomass and chlorophyll measurements showed that the cod4 mutation also resulted in an overall reduction in plant growth and chlorophyll content.