Phosphoenolpyruvate Carboxylase Kinase in Tobacco Leaves Is Activated by Light in a Similar but Not Identical Way as in Maize

Abstract

We have previously reported the partial purification of a Ca2+- independent phosphoenolpyruvate carboxylase (PEPC) protein-serine/threonine kinase (PEPC-PK) from illuminated leaves of N-sufficient tobacco (Nicotiana tabacum L.) plants (Y.-H. Wang, R. Chollet [1993] FEBS Lett 328: 215–218). We now report that this C3 PEPC-kinase is reversibly light activated in vivo in a time-dependent manner. As the kinase becomes light activated, the activity and L-malate sensitivity of its target protein increases and decreases, respectively. The light activation of tobacco PEPC-PK is prevented by pretreatment of detached leaves with various photosynthesis and cytosolic protein-synthesis inhibitors. Similarly, specific inhibitors of glutamine synthetase block the light activation of tobacco leaf PEPC-kinase under both photorespiratory and nonphotorespiratory conditions. This striking effect is partially and specifically reversed by exogenous glutamine, whereas it has no apparent effect on the light activation of the maize (Zea mays L.) leaf kinase. Using an in situ “activity-gel” phosphorylation assay, we have identified two major Ca2+-independent PEPC-kinase catalytic polypeptides in illuminated tobacco leaves that have the same molecular masses (approximately 30 and 37 kD) as found in illuminated maize leaves. Collectively, these results indicate that the phosphorylation of PEPC in N-sufficient leaves of tobacco (C3) and maize (C4) is regulated through similar but not identical light-signal transduction pathways.

Effect of soil nitrogen supply on carbon assimilation by tree stems

“…In leaves, PEP carboxylase is activated under illumination, following its phosphorylation by a light-sensitive PEP carboxylase kinase (see e.g. Li et al, 1996). To confirm the important role of the enzyme in stem carbon assimilation, it would be interesting to examine if the stem PEP carboxylase can be activated under illumination, as is the case in leaves.…”

Pyruvate,Orthophosphate Dikinase in Leaves and Chloroplasts of C3 Plants Undergoes Light-/Dark-Induced Reversible Phosphorylation

“…Less obvious for this hypothesis has been the C 3 origins of proteins that up-/down-regulate certain "target" enzymes in the C 4 pathway. As discussed above, PpcK and PEPc phosphatase, the opposing C 4 PEPc regulatory enzymes, are now known to function in the reversible phosphorylation of non-photosynthetic PEPc in C 3 plants (Duff and Chollet, 1995;Zhang et al, 1995;Li et al, 1996). Based on the evidence gathered in this study, we propose that a C 3 precursor to C 4 RP, or a related RP-like activity, is present in chloroplasts of C 3 plants and functions similarly in the light/dark regulation of C 3 PPDK activity.…”

“…Both of these "converter" enzymes can be found across the spectrum of C 4 species and so must be assumed not to have evolved de novo each time PEPc acquired its photosynthetic role. This has now been inferred by several reports that have characterized the reversible phosphorylation of PEPc in various tissues of C 3 plants, especially during its role in C/N metabolism (Duff and Chollet, 1995;Zhang et al, 1995;Li et al, 1996). Further, C 3 leaf PpcK has been linked to a complex signaling pathway that includes a light/ dark regulatory component (Li et al, 1996), which is also the primary regulatory function this Ser/Thr kinase fulfills in controlling C 4 PEPc (Vidal and Chollet, 1997).…”

“…This has now been inferred by several reports that have characterized the reversible phosphorylation of PEPc in various tissues of C 3 plants, especially during its role in C/N metabolism (Duff and Chollet, 1995;Zhang et al, 1995;Li et al, 1996). Further, C 3 leaf PpcK has been linked to a complex signaling pathway that includes a light/ dark regulatory component (Li et al, 1996), which is also the primary regulatory function this Ser/Thr kinase fulfills in controlling C 4 PEPc (Vidal and Chollet, 1997). In this report, we provide evidence that the C 3 precursor to another C 4 regulatory "converter" enzyme, PPDK-RP, or an RP-like activity, functions in chloroplasts of C 3 leaves.…”

Plant, cell, and molecular mechanisms of abscisic-acid regulation of stomatal apertures. In vivo phosphorylation of phosphoenolpyruvate carboxylase in guard cells of Vicia faba L. is enhanced by fusicoccin and suppressed by abscisic acid

“…However, in other work (20, and references in 21), kinetics modifications indicating regulatory phosphorylation of C3-leaf PEPC were not demonstrated. A detailed explanation of the possible reasons for this apparent discrepancy can be found in (21).…”