The evolution of C<sub>4</sub>photosynthesis
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Abstract
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. Contents Summary 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 365 Acknowledgements 365 References 365
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The record
- Venue
- New Phytologist
- Topic
- Photosynthetic Processes and Mechanisms
- Field
- Biochemistry, Genetics and Molecular Biology
- Canadian institutions
- University of Toronto
- Funders
- —
- Keywords
- PhotorespirationPhotosynthesisBiologyC4 photosynthesisRuBisCOBotanySalinityEcology
- Has abstract in OpenAlex
- yes