期刊
FRONTIERS IN PLANT SCIENCE
卷 7, 期 -, 页码 -出版社
FRONTIERS MEDIA SA
DOI: 10.3389/fpls.2016.00218
关键词
proton gradient; chloroplast; thylakoid; envelope; cation/H plus exchanger
资金
- ERDP from the Ministry of Economy and Competitiveness [BIO2012-33655]
- Junta de Andalucia [CV1-7558]
- NSF [10S- 1553506]
- School of Biological Sciences
- College of Arts and Sciences at Washington State University
- Agricultural Research for Development Fund (ARDF, Egypt)
- Direct For Biological Sciences
- Division Of Integrative Organismal Systems [1553506] Funding Source: National Science Foundation
Proton gradients are fundamental to chloroplast function. Across thylakoid membranes, the light induced-proton gradient is essential for ATP synthesis. As a result of proton pumping into the thylakoid lumen, an alkaline stromal pH develops, which is required for full activation of pH-dependent Calvin Benson cycle enzymes. This implies that a pH gradient between the cytosol (pH 7) and the stroma (pH 8) is established upon illumination. To maintain this pH gradient chloroplasts actively extrude protons. More than 30 years ago it was already established that these proton fluxes are electrically counterbalanced by Mg2+, K+, or Cl fluxes, but only recently the first transport systems that regulate the pH gradient were identified. Notably several (Na,K)/H+ antiporter systems where identified, that play a role in pH gradient regulation, ion homeostasis, osmoregulation, or coupling of secondary active transport. The established pH gradients are important to drive uptake of essential ions and solutes, but not many transporters involved have been identified to date. In this mini review we summarize the current status in the field and the open questions that need to be addressed in order to understand how pH gradients are maintained, how this is interconnected with other transport processes and what this means for chloroplast function.
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