Plant adaptation or acclimation to rising CO₂ ? Insight from first multigenerational RNA-Seq transcriptome

Area of Science:

• Plant evolutionary biology
• Genomics
• Climate change adaptation

Background:

• Atmospheric carbon dioxide (CO2) influences plant photosynthesis, productivity, and fitness.
• CO2 may act as a selective pressure driving plant evolution, but evidence is limited.
• Understanding plant responses to elevated CO2 is crucial for predicting future ecosystems.

Purpose of the Study:

• To investigate the multigenerational response of Plantago lanceolata to elevated atmospheric CO2.
• To characterize the functional and population genomics of plant acclimation and adaptation to high CO2.
• To identify the molecular basis of plant adaptation to increased CO2 levels.

Main Methods:

• Collected Plantago lanceolata seeds from a natural high CO2 spring and an ambient CO2 control site.
• Grew plants in controlled ambient or elevated CO2 conditions (700 μmol mol⁻¹).
• Analyzed phenotypic plasticity, gene expression (transcriptome), and population genomics.

Main Results:

• Significant differences in phenotypic plasticity (biomass, leaf size, stomatal traits) between spring and control plants.
• Modest gene expression changes for acclimation (33-131 differentially expressed genes) but larger changes for adaptation (689-853 DE genes).
• Near-zero genetic differentiation between populations, suggesting adaptation occurs via gene expression rather than fixed genetic changes.
• Identified altered expression of stomatal patterning genes (YODA, CDKB1;1, SCRM2) associated with increased stomatal index in high CO2.
• Observed transcriptome reprogramming of photosynthesis and respiration, with enhanced growth in spring plants.

Conclusions:

• Plantago lanceolata exhibits adaptation to elevated CO2 primarily through gene expression changes, not genetic differentiation.
• Upregulation of stomatal regulators SCRM2 and CDKB1;1 are key controllers of stomatal adaptation to high CO2.
• This study provides insights into the molecular mechanisms underlying plant adaptation to future high CO2 environments.