Calcium oxalate crystal morphology mutants from Medicago truncatula

Abstract

Plants accumulate crystals of calcium oxalate in a variety of shapes and sizes. The mechanism(s) through which a plant defines the morphology of its crystals remains unknown. To gain insight into the mechanisms regulating crystal shapes, we conducted a mutant screen to identify the genetic determinants. This is the first reported mutant screen dedicated to the identification of crystal morphology mutants. A single leaf was harvested from individual Medicago truncatula L. plants that had been chemically mutagenized. Each leaf was visually inspected, using crossed-polarized light microscopy, for alterations in crystal shape and size. Seven different crystal morphology defective ( cmd) mutants were identified. Six cmd mutants were recessive and one dominant. Genetic analysis of the six recessive mutants suggested that each mutant was affected at a different locus. Each cmd mutant represents a new locus different than any previously identified. The plant phenotype of the cmd mutants appeared similar to that of the wild type in overall growth and development. This observation, coupled with the finding that several of the mutants had drastically altered the amount of calcium they partition into the oxalate crystal, questions current hypotheses regarding crystal function. Comparisons between the mutant crystals and those present in other legumes indicated the likelihood that simple point mutations contributed to the evolution of the variations in prismatic crystal shapes commonly observed in these plants today. The availability of cmd mutants provides the opportunity to investigate aspects of crystal shape and size that have been recalcitrant to previous approaches.

Spatio-temporal assembly of functional mineral scaffolds within microbial biofilms

“…29 Their relative growth rates in the various directions may affect crystal shape and its morphology, and may be affected by the biogenic (organic) environment, 30 and with the organic polymeric substances. 31 Since each extracellular matrix mutant has a specific effect on the production of biologically secreted macromolecules, the analysis of crystal morphology in the different matrix mutants can facilitate characterisation of the nature of interactions between the macromolecules and the mineral phase. To this end, crystals were collected, washed and analysed using environmental scanning electron microscopy (ESEM).…”

Biofortification of crops with seven mineral elements often lacking in human diets – iron, zinc, copper, calcium, magnesium, selenium and iodine

“…In plants that precipitate Ca‐oxalate, the accumulation of oxalate is directly proportional to tissue Ca concentration and is, therefore, strongly dependent upon Ca phytoavailability and plant growth rate (Libert & Franceschi, 1987; Kinzel & Lechner, 1992; Franceschi & Nakata, 2005). Some within‐species genetic variation in oxalate concentrations has been observed in beet (Libert & Franceschi, 1987), spinach (Kitchen et al ., 1964; Libert & Franceschi, 1987; Kawazu et al ., 2003; Mou, 2008), rhubarb (Libert & Creed, 1985; Libert, 1987; Libert & Franceschi, 1987), carambola (Wilson et al ., 1982), oca (Ross et al ., 1999; Albihn & Savage, 2001; Sangketkit et al ., 2001), taro (Tanaka et al ., 2003) and soybean (Massey et al ., 2001; Horner et al ., 2005), and several mutants have been identified in the forage legume Medicago truncatula with reduced or altered accumulation of Ca‐oxalate in their leaves (Nakata & McConn, 2000; McConn & Nakata, 2002). For two of the M. truncatula calcium oxalate deficient mutants ( cod5 and cod6 ), reduced accumulation of Ca‐oxalate has been correlated with increased Ca bioavailability in herbage (Nakata & McConn, 2006, 2007; Morris et al ., 2007).…”

Medicago truncatula Mutants Demonstrate the Role of Plant Calcium Oxalate Crystals as an Effective Defense against Chewing Insects

“…This annual diploid species is a relative of the forage crop alfalfa (Medicago sativa). Characteristics of mutant lines of M. truncatula with altered crystal formation demonstrate the genetic control of crystal formation (Nakata and McConn, 2000;McConn and Nakata, 2002). The nonallelic mutations in the calcium oxalate-defective (cod) lines cod5 and cod6 result in severely reduced levels of calcium oxalate compared with those in the parental wild-type line A17, although levels of total calcium in each line are not substantially different (Nakata and McConn, 2000).…”