ARS | Publication request: GENETIC ANALYSIS OF CALCIUM OXALATE CRYSTAL FORMATION IN PLANTS.

Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 9, 2000
Publication Date: N/A

Interpretive Summary: We know that plants accumulate crystals of calcium oxalate in various sizes and areas, but we do not know much about how these crystals form or function. In this report, we present the development of the first genetic screening system to examine calcium oxalate crystal formation in a plant. We used a type of plant that is similar to alfalfa for our study purposes. This system provides researchers with a very important model of analysis for future studies, because we want to figure out how to manipulate edible plants (like spinach, which has a lot of calcium that is not bioavailable)to provide more absorbable nutrients to human beings. Basically, we want to manipulate plants so that more of the calcium they contain is absorbed by people, because less of it is tied up in crystals. Also, we want to eliminate potentially harmful compounds like oxalate, because it is suspected to lead to kidney stone formation. The researchers in this study achieved success in screening leaves from mutant plants with a wide spectrum of alterations in crystal formation.

Technical Abstract: Plants accumulate crystals of calcium oxalate in a variety of shapes, sizes, amounts, and spatial locations. How and why many plants form crystals of calcium oxalate remain largely unknown. To gain insight into the regulatory mechanisms of crystal formation and function, we have developed a mutant screen to identify the genetic determinants. Leaves from a chemically mutagenized Medicago truncatula population were visually screened for alterations in calcium oxalate crystal formation. Seven different classes of calcium oxalate defective (cod) mutants were identified that exhibited alterations in crystal nucleation, morphology, distribution and/or amount. Genetic analysis suggested that crystal formation is a complex process involving more than seven loci. Phenotypic analysis of a mutant that lacks crystals, cod 5, did not reveal any difference in plant growth and development compared to controls. This finding brings into question the hypothesized roles of calcium oxalate formation in supporting tissue structure and in regulating excess tissue calcium.