Regulation of Oxaloacetate, Aspartate, and Malate Formation in Mesophyll Protoplast Extracts of Three Types of C4 Plants

AUTOR(ES)

Huber, Steven C.

RESUMO

The use of mesophyll protoplast extracts from various C4 species has provided an effective method for studying light-and substrate-dependent formation of oxaloacetate, malate, and asparate at rates equivalent to whole leaf C4 photosynthesis. Conditions regulating the formation of the C4 acids were studied with protoplast extracts from Digitaria sanguinalis, an NADP-malic enzyme C4 species, Eleusineindica, an NAD-malic enzyme C4 species, and Urochloa panicoides, a phosphoenolpyruvate (PEP) carboxykinase C4 species. Light-dependent induction of CO2 fixation by the mesophyll extracts of all three species was relatively low without addition of exogenous substrates. Pyruvate, alanine and α-ketoglutarate, or 3-phosphoglycerate induced high rates of CO2 fixation in the mesophyll extracts with oxaloacetate, malate, and aspartate being the primary products. In all three species, it appears that pyruvate, alanine, or 3-phosphoglycerate may serve as effective precursors to the formation of PEP for carboxylation through PEP-carboxylase in C4 mesophyll cells. Induction by pyruvate or alanine and α-ketoglutarate was light-dependent, whereas 3-phosphoglycerate-induced CO2 fixation was not.

Documentos Relacionados

• C4 Photosynthesis: Light-dependent CO2 Fixation by Mesophyll Cells, Protoplasts, and Protoplast Extracts of Digitaria sanguinalis1
• Regulation of Malate Oxidation in Isolated Mung Bean Mitochondria: I. Effects of Oxaloacetate, Pyruvate, and Thiamine Pyrophosphate 12
• Photophosphorylation by Mesophyll and Bundle Sheath Chloroplasts of C4 Plants
• Distribution of Nitrate-assimilating Enzymes between Mesophyll Protoplasts and Bundle Sheath Cells in Leaves of Three Groups of C4 Plants 1
• Regulation of Photosynthesis in C3 and C4 Plants: A Molecular Approach.