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Regulatory Phosphorylation of C4 Phosphoenolpyruvate Carboxylase (A Cardinal Event Influencing the Photosynthesis Rate in Sorghum and Maize).

Abstract：

:C4 leaf phosphoenolpyruvate carboxylase (PEPC; EC 4.1.1.31) is subject to a day/night regulatory phosphorylation cycle. By using the cytoplasmic protein synthesis inhibitor cycloheximide (CHX), we previously reported that the reversible in vivo light activation of the C4 PEPC protein-serine kinase requires protein synthesis. In the present leaf gas-exchange study, we have examined how and to what extent the CHX-induced inhibition of PEPC protein kinase activity/PEPC phosphorylation in the light influences C4 photosynthesis. Detached Sorghum vulgare and maize (Zea mays) leaves fed 10 [mu]M CHX showed a gradual but marked decrease in photosynthetic CO2 assimilation capacity. A series of control experiments designed to assess deleterious secondary effects of the inhibitor established that this reduction in C4 leaf CO2 assimilation was not due to (a) an increased stomatal resistance to CO2 diffusion, (b) a decrease in the activation state of other photoactivated C4 cycle enzymes, and (c) a perturbation of the Benson-Calvin C3 cycle, as evidenced by the absence of an inhibitory effect of CHX on leaf photosynthesis by a C3 grass (Triticum aestivum). It is notable that the CHX-induced decrease in CO2 assimilation by illuminated Sorghum leaves was highly correlated with a decrease in the apparent phosphorylation status of PEPC and a concomitant change in carbon isotope discrimination consistent with a shift from a C4 to a C3 mode of leaf CO2 fixation. These collective findings indicate that the light-dependent activation of the PEPC protein-serine kinase and the resulting phosphorylation of serine-8 or serine-15 in Sorghum or maize PEPC, respectively, are fundamental regulatory events that influence leaf C4 photosynthesis in vivo.

journal_name

Plant Physiol

journal_title

Plant physiology

authors

Bakrim N,Prioul JL,Deleens E,Rocher JP,Arrio-Dupont M,Vidal J,Gadal P,Chollet R

doi

10.1104/pp.101.3.891

subject

Has Abstract

pub_date

1993-03-01 00:00:00

pages

891-897

issue

eissn

0032-0889

issn

1532-2548

pii

101/3/891

journal_volume

101

pub_type

杂志文章

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Regulatory Phosphorylation of C4 Phosphoenolpyruvate Carboxylase (A Cardinal Event Influencing the Photosynthesis Rate in Sorghum and Maize).