Meeting in the Middle: Lessons and Opportunities from Studying C3-C4Intermediates

Mae Antonette Mercado, Anthony J. Studer

Research output: Contribution to journalReview articlepeer-review


The discovery of C3-C4 intermediate species nearly 50 years ago opened up a new avenue for studying the evolution of photosynthetic pathways. Intermediate species exhibit anatomical, biochemical, and physiological traits that range from C3 to C4. A key feature of C3-C4 intermediates that utilize C2 photosynthesis is the improvement in photosynthetic efficiency compared with C3 species. Although the recruitment of some core enzymes is shared across lineages, there is significant variability in gene expression patterns, consistent with models that suggest numerous evolutionary paths from C3 to C4 photosynthesis. Despite the many evolutionary trajectories, the recruitment of glycine decarboxylase for C2 photosynthesis is likely required. As technologies enable high-throughput genotyping and phenotyping, the discovery of new C3-C4 intermediates species will enrich comparisons between evolutionary lineages. The investigation of C3-C4 intermediate species will enhance our understanding of photosynthetic mechanisms and evolutionary processes and will potentially aid in crop improvement.

Original languageEnglish (US)
Pages (from-to)43-65
Number of pages23
JournalAnnual Review of Plant Biology
StatePublished - 2022


  • C-Cintermediate
  • Cphotosynthesis
  • interspecific hybrids
  • photorespiratory glycine shuttle
  • trait evolution

ASJC Scopus subject areas

  • Molecular Biology
  • Physiology
  • Plant Science
  • Cell Biology


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