Dynamic regulatory control of plant heteromeric ACCase revealed by spatiotemporal stoichiometry.

In Arabidopsis thaliana, plastid hetACCase catalytic subunits show nearly 1:1:1 in vivo stoichiometry across organs and conditions, while regulatory effectors vary tissue-specifically.

• Why it matters: hetACCase is regulated by multiple protein classes, but its absolute protein stoichiometry across development and light has been unclear, limiting understanding of how regulation is coordinated.
• What they did: The authors expanded an AQUA-MRM assay to quantify absolute abundance of hetACCase catalytic subunits and effectors across Arabidopsis organs, developmental stages, and light conditions.
• The result: β-CT accumulated highest (112 fmol/µg at 11 DAF seed), catalytic subunits BC/BCCP/α-CT were structurally coordinated, and effectors (PII, CTI, BADC) often exceeded catalytic subunits with distinct tissue peaks and light-onset responses.