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ARS Home » Plains Area » Fargo, North Dakota » Edward T. Schafer Agricultural Research Center » Sugarbeet and Potato Research » Research » Publications at this Location » Publication #337497
Title: Glycolysis is dynamic and relates closely to respiration rate in stored sugarbeet roots

Author
item MEGGUER, CLARICE - Universidade Federal De Vicosa
item Fugate, Karen
item LAFTA, ABBAS - North Dakota State University
item FERRAREZE, JOCLEITA - Universidade Federal De Vicosa
item DECKARD, EDWARD - North Dakota State University
item Campbell, Larry
item Lulai, Edward
item FINGER, FERNANDO - Universidade Federal De Vicosa

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/9/2017
Publication Date: 5/24/2017
Citation: Megguer, C.A., Fugate, K.K., Lafta, A.M., Ferrareze, J.P., Deckard, E.L., Campbell, L.G., Lulai, E.C., Finger, F.L. 2017. Glycolysis is dynamic and relates closely to respiration rate in stored sugarbeet roots. Frontiers in Plant Science. doi: 10.3389/fpls.2017.00861.

Interpretive Summary: Although respiration is the principal cause of sucrose loss in stored sugarbeet roots, the mechanisms that control sugarbeet root respiration have not been established. Available evidence, however, indicates that respiration is likely to be controlled by the availability of the carbon compounds that fuel respiration, and glycolysis has a central role in generating these compounds. Research was conducted to characterize glycolysis in sugarbeet roots after harvest and during storage and to investigate relationships between glycolysis and root respiration rate. Glycolysis was highly variable during storage, with 10 of 14 of the enzymes that contribute to glycolysis and 14 of 17 of the metabolites involved in glycolysis significantly altered during 60 d in storage. Changes in glycolysis were greatest in the first 4 days of storage, but also occurred throughout the 60 d storage period. Similarities between glycolysis and root respiration rate were abundant, with 10 of 14 of the enzymes activities that contribute to glycolysis elevated when root respiration was elevated and nine glycolytic enzyme activities static during periods of unchanging respiration rate. Although all glycolytic enzymes are likely to contribute in varying degrees to the regulation of glycolysis, major roles for the enzymes pyruvate kinase and phosphofructokinase were indicated in the regulation of sugarbeet root glycolysis during storage. Overall, these results establish that glycolysis is not static during sugarbeet root storage, that changes in glycolysis are closely related to changes in sugarbeet root respiration, and that glycolysis restricts root respiration, responds to respiratory demand, or is regulated similarly to respiration rate in stored sugarbeet roots.

Technical Abstract: Although respiration is the principal cause of postharvest sugarbeet (Beta vulgaris L.) sucrose loss, the internal mechanisms that control sugarbeet root respiration have not been established. Available evidence, however, indicates that respiration is likely to be controlled by the availability of respiratory substrates, and glycolysis has a central role in generating these substrates. To determine glycolytic changes that occur in sugarbeet roots after harvest and during storage and to elucidate relationships between glycolysis and respiration, sugarbeet roots were stored for up to 60 d, during which the activities of glycolytic enzymes and the concentrations of glycolytic substrates, intermediates, cofactors, and products were determined. Respiration rate was also determined, and relationships between respiration rate and glycolytic enzymes and metabolites were determined. Glycolysis was highly variable during storage, with 10 of 14 glycolytic activities and 14 of 17 glycolytic metabolites significantly altered during the 60 d after harvest. Changes in glycolytic enzyme activities and metabolites were greatest in the first four days of storage, but also occurred throughout the 60 d storage period. Similarities between changes in glycolytic enzyme activities and root respiration rate were abundant, with 10 of 14 enzyme activities elevated when root respiration was elevated and nine glycolytic activities static during periods of unchanging respiration rate. Although all glycolytic enzymes are likely to contribute in varying degrees to the regulation of glycolytic flux, changes in enzyme activities and concentrations of their substrates and products indicated major roles for pyruvate kinase and phosphofructokinase in the regulation of postharvest sugarbeet root glycolysis. Additionally, correlation and principal component analysis revealed a strong positive relationship between changes in respiration rate and changes in pyruvate kinase activity, suggesting that downstream TCA cycle enzymes are unlikely to majorly restrict or regulate root respiration. Overall, these results establish that glycolysis is not static during sugarbeet root storage and that changes in glycolysis are closely related to changes in sugarbeet root respiration. It is likely, therefore, that glycolysis restricts root respiration, responds to respiratory substrate demand, or is regulated similarly to respiration rate in postharvest sugarbeet roots.