SUCROSE ACCUMULATION AND RETENTION IN SUGARBEETS
Location: Sugarbeet and Potato Research
Title: Metabolic changes associated with elevated respiration rate in stored sugarbeet roots after injury
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: November 1, 2010
Publication Date: June 1, 2011
Citation: Lafta, A.M., Fugate, K.K. 2011. Metabolic changes associated with elevated respiration rate in stored sugarbeet roots after injury [abstract.] Journal of Sugar Beet Research. 48:74.
Although respiration is estimated to cause 60 to 80% of the sucrose loss that occurs during storage, the mechanisms controlling sugarbeet root respiration rate are unknown. Previous research suggested that sugarbeet root respiration was limited by the availability of respiratory substrates, which are synthesized from sucrose by the combined action of sucrose-degrading enzymes, the glycolytic pathway, and the tricarboxylic acid cycle (TCA). To identify possible restrictions in these pathways that may limit respiratory substrate availability and thereby limit respiration, changes in the concentration of compounds that are substrates, intermediates, or cofactors in the respiratory pathway were quantified in roots whose respiration was elevated by injury. In wounded tissue, respiration increased an average of 186%, fructose, glucose 6-phosphate, ADP and UDP concentrations increased, and fructose 1,6-bisphosphate, triose phosphate, citrate, isocitrate, succinate, ATP, UTP and NAD+ concentrations decreased. In the nonwounded tissue of wounded roots, respiration rate increased an average of 21%, glucose 6-phosphate, fructose 6-phosphate, glucose 1-phosphate and ADP concentrations increased, and isocitrate, UTP, NAD+, NADP+, and NADPH concentrations declined. In wounded tissue, the data suggests that activities of early glycolytic enzymes limited carbon flow through glycolysis, although these restrictions were likely overcome by use of metabolic bypasses that allowed carbon compounds to enter the pathway at glycolytic and TCA cycle downstream locations. In nonwounded tissue, the data suggests that glycolysis and the TCA cycle were generally capable of supporting small elevations in respiration rate. Although the mechanism by which respiration is regulated in wounded sugarbeet roots is unknown, localized and systemic elevations in respiration were positively associated with one or more indicators of cellular redox status.