Submitted to: Plant Physiology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/24/2013
Publication Date: 2/14/2013
Publication URL: http://handle.nal.usda.gov/10113/58005
Citation: Lisko, K.A., Hubstenberger, J.F., Phillips, G.C., Miller, H.B., McClung, A.M., Lorence, A. 2013. Ontogenetic changes in vitamin C in selected rice varieties. Plant Physiology and Biochemistry. 66:41-46. Interpretive Summary: As a result of both biotic and abiotic stresses, plants produce excessive compounds called reactive oxygen species (ROS) which are toxic to cells and cause irreparable damage. Plants keep ROS levels under control using the antioxidant Vitamin C (L-ascorbic acid). No plant completely devoid of Vitamin C has ever been reported, indicating the key function of this molecule for plant survival and health. Arabidopsis thaliana is model plant species that has served as the basis for much of what we know about Vitamin C metabolism in plants. In this study, we evaluated 22 rice cultivars and two weedy rice accessions to determine if they vary in the timing and amount of Vitamin C produced in plant tissue. Results demonstrated that the amount of Vitamin C produced in rice peaked at an early vegetative stage and then at flowering, in contrast to Arabidopsis where it has been reported to decline as the plant ages. In addition, significant differences were observed among the rice accessions for Vitamin C content. These results demonstrate that the plant stage and choice of cultivar can greatly impact Vitamin C determination in rice. Future research will be conducted to determine if Vitamin C content in rice varies in response to biotic or abiotic stress.
Technical Abstract: Vitamin C (L-ascorbic acid, AsA) is a key antioxidant for both plants and animals. In plants, AsA is involved in several key physiological processes including photosynthesis, cell expansion, cell division, growth, flowering, and senescence. In addition, AsA is an enzyme cofactor and a regulator of gene expression. During exposure to abiotic stresses, AsA counteracts excessive reactive oxygen species within the cell and protects key molecules, including lipids, proteins, and nucleic acids, from irreversible damage. In this study we focus on understanding how vitamin C levels are controlled in rice (Oryza sativa) during plant development. Our results indicate that in rice ascorbate metabolism follows a unique pattern compared to other species. The steady state AsA level was measured in six rice accessions. In all of these, the total foliar AsA content increases during development and peaks at the vegetative 2 (V2) and the reproductive 4 (R4) stages, whereas in Arabidopsis thaliana and other dicots, foliar AsA content declines with plant age. Foliar AsA content in rice does not seem to increase as the light period progresses, as happens in Arabidopsis. The total foliar AsA content of twenty-four rice accessions from all five major rice subgroups were compared. The accessions differed significantly in their AsA content at the V2 stage, indicating the potential to enhance vitamin C levels in accessions of regional interest via breeding approaches.