Universität zu Köln

Kunz, Hans-Henning, Gierth, Markus, Herdean, Andrei ORCID: 0000-0003-2143-0213, Satoh-Cruz, Mio, Kramer, David M., Spetea, Cornelia and Schroeder, Julian I. (2014). Plastidial transporters KEA1, -2, and -3 are essential for chloroplast osmoregulation, integrity, and pH regulation in Arabidopsis. Proc. Natl. Acad. Sci. U. S. A., 111 (20). S. 7480 - 7486. WASHINGTON: NATL ACAD SCIENCES. ISSN 0027-8424

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Abstract

K+ transporters and channels and the corresponding mutants have been described and studied in the plasma membrane and organelle membranes of plant cells. However, knowledge about the molecular identity of chloroplast K+ transporters is limited. Potassium transport and a well-balanced K+ homeostasis were suggested to play important roles in chloroplast function. Because no loss-of-function mutants have been identified, the importance of K+ transporters for chloroplast function and photosynthesis remains to be determined. Here, we report single and higher-order loss-of-function mutants in members of the cation/proton antiporters-2 antiporter superfamily KEA1, KEA2, and KEA3. KEA1 and KEA2 proteins are targeted to the inner envelope membrane of chloroplasts, whereas KEA3 is targeted to the thylakoid membrane. Higher-order but not single mutants showed increasingly impaired photosynthesis along with pale green leaves and severely stunted growth. The pH component of the proton motive force across the thylakoid membrane was significantly decreased in the kea1kea2 mutants, but increased in the kea3 mutant, indicating an altered chloroplast pH homeostasis. Electron microscopy of kea1kea2 leaf cells revealed dramatically swollen chloroplasts with disrupted envelope membranes and reduced thylakoid membrane density. Unexpectedly, exogenous NaCl application reversed the observed phenotypes. Furthermore, the kea1kea2 background enables genetic analyses of the functional significance of other chloroplast transporters as exemplified here in kea1kea2Na(+)/H+ antiporter1 (nhd1) triple mutants. Taken together, the presented data demonstrate a fundamental role of inner envelope KEA1 and KEA2 and thylakoid KEA3 transporters in chloroplast osmoregulation, integrity, and ion and pH homeostasis.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Kunz, Hans-Henning UNSPECIFIED UNSPECIFIED UNSPECIFIED Gierth, Markus UNSPECIFIED UNSPECIFIED UNSPECIFIED Herdean, Andrei UNSPECIFIED orcid.org/0000-0003-2143-0213 UNSPECIFIED Satoh-Cruz, Mio UNSPECIFIED UNSPECIFIED UNSPECIFIED Kramer, David M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Spetea, Cornelia UNSPECIFIED UNSPECIFIED UNSPECIFIED Schroeder, Julian I. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-438187
DOI:	10.1073/pnas.1323899111
Journal or Publication Title:	Proc. Natl. Acad. Sci. U. S. A.
Volume:	111
Number:	20
Page Range:	S. 7480 - 7486
Date:	2014
Publisher:	NATL ACAD SCIENCES
Place of Publication:	WASHINGTON
ISSN:	0027-8424
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language INNER-ENVELOPE; INTACT CHLOROPLASTS; K+ TRANSPORTERS; HIGHER-PLANTS; ION CHANNELS; HOMEOSTASIS; GROWTH; LIGHT; PHOTOSYNTHESIS; ANTIPORTERS Multiple languages Multidisciplinary Sciences Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/43818