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- Title
Involvement of phospholipase D and phosphatidic acid in the light-dependent up-regulation of sorghum leaf phosphoenolpyruvate carboxylase-kinase.
- Authors
Monreal, José Antonio; López-Baena, Francisco Javier; Vidal, Jean; Echevarría, Cristina; García-Mauriño, Sofía
- Abstract
The photosynthetic phosphoenolpyruvate carboxylase (C4-PEPC) is regulated by phosphorylation by a phosphoenolpyruvate carboxylase kinase (PEPC-k). In Digitaria sanguinalis mesophyll protoplasts, this light-mediated transduction cascade principally requires a phosphoinositide-specific phospholipase C (PI-PLC) and a Ca2+-dependent step. The present study investigates the cascade components at the higher integrated level of Sorghum bicolor leaf discs and leaves. PEPC-k up-regulation required light and photosynthetic electron transport. However, the PI-PLC inhibitor U-73122 and inhibitors of calcium release from intracellular stores only partially blocked this process. Analysis of [32P]phosphate-labelled phospholipids showed a light-dependent increase in phospholipase D (PLD) activity. Treatment of leaf discs with n-butanol, which decreases the formation of phosphatidic acid (PA) by PLD, led to the partial inhibition of the C4-PEPC phosphorylation, suggesting the participation of PLD/PA in the signalling cascade. PPCK1 gene expression was strictly light-dependent. Addition of neomycin or n-butanol decreased, and a combination of both inhibitors markedly reduced PPCK1 expression and the concomitant rise in PEPC-k activity. The calcium/calmodulin antagonist W7 blocked the light-dependent up-regulation of PEPC-k, pointing to a Ca2+-dependent protein kinase (CDPK) integrating both second messengers, calcium and PA, which were shown to increase the activity of sorghum CDPK.
- Subjects
PROTEIN kinases; CRABGRASS; PHOSPHORYLATION; PHOSPHOLIPASE C; SORGHUM; CALCIUM ions
- Publication
Journal of Experimental Botany, 2010, Vol 61, Issue 10, p2819
- ISSN
0022-0957
- Publication type
Article
- DOI
10.1093/jxb/erq114