ARS | Publication request: THE ROLE OF CALCIUM OXALATE CRYSTALS IN MEDICAGO TRUNCATULA DEFENSE AGAINST CHEWING INSECTS.

Submitted to: American Society of Plant Biologists Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: February 28, 2005
Publication Date: July 16, 2005
Citation: Park, S., Wang, Q., Nakata, P.A., Korth, K. 2005. The role of calcium oxalate crystals in Medicago truncatula defense against chewing insects [abstract]. American Society of Plant Biologists Annual Meeting. p. 157.

Technical Abstract: Calcium oxalate crystals are the most common insoluble mineral found in plants and can appear in different sizes and shapes. Functions proposed for the crystals include roles in ion balance, tissue support, detoxification, and in light-gathering and -reflection. We use calcium oxalate defective (cod) lines of M. truncatula to assess effects of plant calcium oxalate crystals on the survival of chewing insects. In cod5 and cod6 mutants, leaves contain far fewer crystals and the crystals present are smaller and more globular in shape than in the wildtype line, A17. Results indicate that Spodoptera exigua (beet armyworm) larvae that feed on low levels of commercial calcium oxalate crystals grow faster and have a higher survival rate than larvae that feed on high levels of commercial calcium oxalate crystals. Observation of insect mandibles via scanning electron microscopy shows that mandibles of S. exigua larvae that feed on wildtype A17 are more worn than those of larvae that feed on cod mutants or artificial diet. Furthermore, RNA blot analysis shows that wound-inducible transcripts respond normally in cod mutants, indicating that the mutant plant lines are not defective in recognition of, or induced response to, insect herbivores. We assayed gene expression patterns in response to herbivory in cod5 mutants using microarray analysis. Results indicate that several genes are differentially up- or down-regulated after insect herbivory. If calcium oxalate crystals serve as a deterrent to herbivory by insects, then learning how they are made could lead to a strategy for improving pest control in crops.