Altering hemoglobin levels changes energy status in maize cells under hypoxia

Nonsymbiotic hemoglobins are broadly present across the plant kingdom; however, the function of these proteins is unknown. Cultured maize cells have been transformed to constitutively express a barley hemoglobin gene in either the sense (HB+) or antisense (HB-) orientation. Hemoglobin protein in the...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1998-08, Vol.95 (17), p.10317-10321
Main Authors: Sowa, A.W. (University of Manitoba, Winnipeg, MB, Canada.), Duff, S.M.G, Guy, P.A, Hill, R.D
Format: Article
Language:English
Subjects:
ACTIVIDAD ENZIMATICA
ACTIVITE ENZYMATIQUE
ADN
ADP
ALCOHOL DEHYDROGENASE
ALCOHOL DESHIDROGENASA
ALCOOL DESHYDROGENASE
AMP
ANTISENSE DNA
ATP
AVAILABILITY
Barley
Biological Sciences
Botany
CARBON DIOXIDE
CELL CULTURE
Cell culture techniques
Cell lines
Cells
CHEMICAL COMPOSITION
COMPLEMENTARY DNA
COMPOSICION QUIMICA
COMPOSITION CHIMIQUE
CONSOMMATION D'OXYGENE
CONSUMO DE OXIGENO
Corn
CULTIVO DE CELULAS
CULTURE DE CELLULE
Cultured cells
DIOXIDO DE CARBONO
DIOXYDE DE CARBONE
DNA
ENZYMIC ACTIVITY
GAS PRODUCTION
GASES
GAZ
GENETIC TRANSFORMATION
HAEMOGLOBIN
HEMOGLOBINA
HEMOGLOBINE
Hemoglobins
HORDEUM VULGARE
Hypoxia
Nitrogen
OXIGENO
OXYGEN
OXYGEN CONSUMPTION
OXYGENE
Plants
Proteins
TRANSFORMACION GENETICA
TRANSFORMATION GENETIQUE
ZEA MAYS
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Summary:Nonsymbiotic hemoglobins are broadly present across the plant kingdom; however, the function of these proteins is unknown. Cultured maize cells have been transformed to constitutively express a barley hemoglobin gene in either the sense (HB+) or antisense (HB-) orientation. Hemoglobin protein in the transformed cell lines correspondingly was higher or lower than in wild-type cells under normal atmospheric conditions. Limiting oxygen availability, by placing the cells in a nitrogen atmosphere for 12 hr, had little effect on the energy status of cells constitutively expressing hemoglobin, but had a pronounced effect on both wild-type and HB- cells, where ATP levels declined by 27% and 61%, respectively. Total adenylates in these cells were approximately 35% lower than in HB+ cells. Energy charge was relatively unaffected by the treatment in HB+ and wild-type cells, but was reduced from 0.91 to 0.73 in HB- cells, suggesting that the latter were incapable of maintaining their energy status under the low oxygen regime. Treatment of the cells grown in an air atmosphere with antimycin A gave essentially the same results. It is suggested that nonsymbiotic hemoglobins act in plants to maintain the energy status of cells in low oxygen environments and that they accomplish this effect by promoting glycolytic flux through NADH oxidation, resulting in increased substrate-level phosphorylation. Hypoxic acclimation of plants is an example of this effect in nature. Nonsymbiotic hemoglobins are likely ancestors of an early form of hemoglobin that sequestered oxygen in low oxygen environments, providing a source of oxygen to oxidize NADH to provide ATP for cell growth and development
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.95.17.10317