Photoprotection conferred by changes in photosynthetic protein levels and organization during dehydration of a homoiochlorophyllous resurrection plant.

Abstract

During desiccation, homoiochlorophyllous resurrection plants retain most of their photosynthetic apparatus, allowing them to resume photosynthetic activity quickly upon water availability. These plants rely on various mechanisms to prevent the formation of reactive oxygen species and/or protect their tissues from the damage they inflict. In this work, we addressed the issue of how homoiochlorophyllous resurrection plants deal with the problem of excessive excitation/electron pressures during dehydration using Craterostigma pumilum as a model plant. To investigate the alterations in the supramolecular organization of photosynthetic protein complexes, we examined cryoimmobilized, freeze-fractured leaf tissues using (cryo)scanning electron microscopy. These examinations revealed rearrangements of photosystem II (PSII) complexes, including a lowered density during moderate dehydration, consistent with a lower level of PSII proteins, as shown by biochemical analyses. The latter also showed a considerable decrease in the level of cytochrome f early during dehydration, suggesting that initial regulation of the inhibition of electron transport is achieved via the cytochrome b6f complex. Upon further dehydration, PSII complexes are observed to arrange into rows and semicrystalline arrays, which correlates with the significant accumulation of sucrose and the appearance of inverted hexagonal lipid phases within the membranes. As opposed to PSII and cytochrome f, the light-harvesting antenna complexes of PSII remain stable throughout the course of dehydration. Altogether, these results, along with photosynthetic activity measurements, suggest that the protection of retained photosynthetic components is achieved, at least in part, via the structural rearrangements of PSII and (likely) light-harvesting antenna complexes into a photochemically quenched state.

• Authors: Dana Charuvi, Reinat Nevo, Eyal Shimoni, Leah Naveh, Ahmad Zia, Zach Adam, Jill M Farrant, Helmut Kirchhoff, Ziv Reich
• Journal: Plant physiology (Plant Physiol) Vol. 167 Issue 4 Pg. 1554-65 (Apr 2015) ISSN: 1532-2548 [Electronic] United States
• PMID: 25713340 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.)
• Copyright: © 2015 American Society of Plant Biologists. All Rights Reserved.

Chemical References

• Photosynthetic Reaction Center Complex Proteins
• Photosystem II Protein Complex
• Plant Proteins
• Water
• Cytochrome b6f Complex

Topics

• Craterostigma (genetics, physiology, radiation effects)
• Cytochrome b6f Complex (genetics, metabolism)
• Dehydration
• Desiccation
• Electron Transport
• Light
• Photosynthesis (physiology)
• Photosynthetic Reaction Center Complex Proteins (genetics, metabolism)
• Photosystem II Protein Complex (metabolism)
• Plant Leaves (genetics, physiology, radiation effects)
• Plant Proteins (genetics, metabolism)
• Water (physiology)