We developed a new method using 13CO2 and mass spectrometry to elucidate the role of photorespiration as an alternative electron dissipating pathway under drought stress. This was achieved by experimentally distinguishing between the CO2 fluxes into and out of the leaf. The method allows us to determine the rates of gross CO2 assimilation and gross CO2 evolution in addition to net CO2 uptake by...

Mitochondrial dihydrolipoyl dehydrogenase (mtLPD; L-protein) is an integral component of several multienzyme systems involved in the tricarboxylic acid (TCA) cycle, photorespiration, and the degradation of branched-chain α-ketoacids. The majority of the mtLPD present in photosynthesizing tissue is used for glycine decarboxylase (GDC), necessary for the high-flux photorespiratory glycine-into-se...

C4 plants evolved independently more than 60 times from C3 ancestors. C4 photosynthesis is a complex trait and its evolution from the ancestral C3 photosynthetic pathway involved the modification of the leaf anatomy and the leaf physiology accompanied by changes in the expression of thousands of genes. Under high temperature, high light, and the current CO2 concentration in the atmosphere, the ...

The process of oxygenic photosynthesis is robust and ubiquitous, relying centrally on input of light, carbon dioxide, and water, which in many environments are all abundantly available, and from which are produced, principally, oxygen and reduced organic carbon. However, photosynthetic machinery can be conflicted by the simultaneous presence of carbon dioxide and oxygen through a process someti...

Glycolic acid has been su,ggested as a major substrate for photorespiration. According to Zelitch (5,6), respiration in the light is several times greater than dark respiration because many plants in the Iiloht synthesize large quantities of glycolic acid which is then oxidized, in 'part at least, to CO2. Yet little glycolic acid is ever found in normal illuminated leaves. If any significant am...

Serine:glyoxylate aminotransferase (SGAT) converts glyoxylate and serine to glycine and hydroxypyruvate during photorespiration. Besides this, SGAT operates with several other substrates including asparagine. The impact of this enzymatic promiscuity on plant metabolism, particularly photorespiration and serine biosynthesis, is poorly understood. We found that elevated SGAT activity causes surpr...

A three-phase discontinuous sucrose gradient yielded two fractions of chloroplast envelope membranes from spinach (Spinacia oleracea L.), sunflower (Helianthus annuus L.), and maize (Zea mays L., mesophyll and undifferentiated chloroplasts). These species were selected to represent plants with fast photorespiration and slow net photosynthesis, fast photorespiration yet fast net photosynthesis, ...

Photorespiration is essential for all organisms performing oxygenic photosynthesis. The evolution of photorespiratory metabolism began among cyanobacteria and led to a highly compartmented pathway in plants. A molecular understanding of photorespiration in eukaryotic algae, such as glaucophytes, rhodophytes, and chlorophytes, is essential to unravel the evolution of this pathway. However, mecha...