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The evolution of C 4 photosynthesis
Author(s) -
Sage Rowan F.
Publication year - 2004
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.2004.00974.x
Subject(s) - photorespiration , photosynthesis , biology , c4 photosynthesis , rubisco , botany , salinity , ecology
Summary C 4 photosynthesis is a series of anatomical and biochemical modifications that concentrate CO 2 around the carboxylating enzyme Rubisco, thereby increasing photosynthetic efficiency in conditions promoting high rates of photorespiration. The C 4 pathway independently evolved over 45 times in 19 families of angiosperms, and thus represents one of the most convergent of evolutionary phenomena. Most origins of C 4 photosynthesis occurred in the dicots, with at least 30 lineages. C 4 photosynthesis first arose in grasses, probably during the Oligocene epoch (24–35 million yr ago). The earliest C 4 dicots are likely members of the Chenopodiaceae dating back 15–21 million yr; however, most C 4 dicot lineages are estimated to have appeared relatively recently, perhaps less than 5 million yr ago. C 4 photosynthesis in the dicots originated in arid regions of low latitude, implicating combined effects of heat, drought and/or salinity as important conditions promoting C 4 evolution. Low atmospheric CO 2 is a significant contributing factor, because it is required for high rates of photorespiration. Consistently, the appearance of C 4 plants in the evolutionary record coincides with periods of increasing global aridification and declining atmospheric CO 2 . Gene duplication followed by neo‐ and nonfunctionalization are the leading mechanisms for creating C 4 genomes, with selection for carbon conservation traits under conditions promoting high photorespiration being the ultimate factor behind the origin of C 4 photosynthesis.ContentsSummary 341 I. Introduction 342 II. What is C 4 photosynthesis? 343 III. Why did C 4 photosynthesis evolve? 347 IV. Evolutionary lineages of C 4 photosynthesis 348 V. Where did C 4 photosynthesis evolve? 350 VI. How did C 4 photosynthesis evolve? 352 VII. Molecular evolution of C 4 photosynthesis 361 VIII. When did C 4 photosynthesis evolve 362 IX. The rise of C 4 photosynthesis in relation to climate and CO 2 363 X. Final thoughts: the future evolution of C 4 photosynthesis 365Acknowledgements 365References 365