This Article Full Text Full Text (PDF) Supplemental Data All Versions of this Article: 136/2/3070    most recent pp.104.047712v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via ISI Web of Science (11) Citing Articles via Google Scholar Google Scholar Articles by Harel, Y. Articles by Kaplan, A. Search for Related Content PubMed PubMed Citation Articles by Harel, Y. Articles by Kaplan, A. Agricola Articles by Harel, Y. Articles by Kaplan, A.

BIOENERGETICS AND PHOTOSYNTHESIS

Activation of Photosynthesis and Resistance to Photoinhibition in Cyanobacteria within Biological Desert Crust^1,[w]

Department of Plant and Environmental Sciences (Y.H., A.K.), Minerva Arid Ecosystems Research Center (Y.H., A.K.), Department of Biological Chemistry (I.O.), and Minerva, Avron-Evenari Center of Photosynthesis Research (I.O., A.K.), The Hebrew University of Jerusalem, Jerusalem, 91014, Israel

Filamentous cyanobacteria are the main primary producers in biological desert sand crusts. The cells are exposed to extreme environmental conditions including temperature, light, and diurnal desiccation/rehydration cycles. We have studied the kinetics of activation of photosynthesis during rehydration of the cyanobacteria, primarily Microcoleus sp., within crust samples collected in the Negev desert, Israel. We also investigated their susceptibility to photoinhibition. Activation of the photosynthetic apparatus, measured by fluorescence kinetics, thermoluminescence, and low temperature fluorescence emission spectra, did not require de novo protein synthesis. Over 50% of the photosystem II (PSII) activity, assembled phycobilisomes, and photosystem I (PSI) antennae were detected within less than 5 min of rehydration. Energy transfer to PSII and PSI by the respective antennae was fully established within 10 to 20 min of rehydration. The activation of a fraction of PSII population (about 20%–30%) was light and temperature-dependent but did not require electron flow to plastoquinone [was not inhibited by 3-(3,4-dichlorophenyl)-1,1-dimethylurea]. The cyanobacteria within the crusts are remarkably resistant to photoinhibition even in the absence of protein synthesis. The rate of PSII repair increased with light intensity and with time of exposure. Consequently, the extent of photoinhibition in high-light-exposed crusts reached a constant, relatively low, level. This is in contrast to model organisms such as Synechocystis sp. strain PCC 6803 where PSII activity declined continuously over the entire exposure to high illumination. Ability of the crust's organisms to rapidly activate photosynthesis upon rehydration and withstand photoinhibition under high light intensity may partly explain their ability to survive in this ecosystem.

^[w] The online version of this article contains Web-only data.

Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.104.047712.

^* Corresponding author; e-mail: aaronka{at}vms.huji.ac.il; fax 972–2–6584463.

Received June 7, 2004; returned for revision July 5, 2004; accepted July 5, 2004.

This article has been cited by other articles:

				P. Alpert The Limits and Frontiers of Desiccation-Tolerant Life Integr. Comp. Biol., November 1, 2005; 45(5): 685 - 695. [Abstract] [Full Text] [PDF]