# Peanut leaf transcriptomic dynamics reveals insights into the acclimation response to elevated carbon dioxide under semiarid conditions

## TL;DR

This study explores how peanut plants adapt at the molecular level to higher carbon dioxide levels in a semiarid environment.

## Contribution

A new method for analyzing gene expression patterns reveals how elevated CO2 influences carbon metabolism in peanut plants.

## Key findings

- Elevated CO2 upregulates light reactions and sucrose synthesis genes during water stress.
- Photorespiration is consistently downregulated under elevated CO2 across all growth stages.
- Starch synthesis genes are activated by elevated CO2 during drought periods.

## Abstract

Elevated atmospheric carbon dioxide [CO2] increases peanut carbon assimilation and productivity. However, the molecular basis of such responses is not well understood. We tested the hypothesis that maintaining high photosynthesis under long-term elevated [CO2] is associated with the shift in C metabolism gene expression regulation.

We used a field CO2 enrichment system to examine the effects of elevated [CO2] (ambient + 250 ppm) across different soil water availability and plant developmental stages on the molecular responses in a peanut runner-type genotype. Plants under both [CO2] treatments were grown in semiarid conditions. We evaluated a comparative leaf transcriptomic profile across three periodic water deficit/re-hydration (well-watered/recovery) cycles throughout the growing season using RNAseq analysis.

Our results showed that the transcriptome responses were influenced by [CO2], water availability, and developmental stages. The traditional Mercator annotation analysis based on percentage total revealed that lipid metabolism, hormone biosynthesis, secondary metabolism, amino acid biosynthesis, and transport were the most regulated biological processes. However, our new approach based on the comparative relative percentage change per individual category across stages revealed new insights into the gene expression patterns of biological functional groups, highlighting the relevance of the C-related pathways regulated by elevated [CO2].

The photosynthesis analysis showed that 1) The light reaction was the most upregulated pathway by elevated [CO2] during water stress, 2) Photorespiration was downregulated across all stages, 3) Sucrose synthesis genes were upregulated by elevated [CO2] before stress, 4) Starch synthesis genes were upregulated by elevated [CO2] under drought periods, and 5) CO2 regulation of sucrose and starch degradation was critical under drought periods. Our findings provide valuable insights into the molecular basis underlying the photosynthetic acclimation response to elevated [CO2] in peanuts.