RNA editing of the cytochrome b6f complex modulates drought response in tomato (Solanum lycopersicum) via distinct cyt f (petA) isoforms

RNA editing is a crucial post-transcriptional mechanism that enables plants to adapt to environmental stress. However, its specific role in remodeling photosynthetic complexes under drought conditions remains unclear. In this study, RNA editing in Solanum lycopersicum (tomato) was investigated during drought stress, focusing on its impact on the cytochrome b 6 f (Cyt b 6 f) complex a key component of the photosynthetic electron transport chain. Findings revealed that editing sites in petA (Cyt f) and petB (Cyt b 6 ) transcripts were dynamically regulated by drought, leading to nucleotide substitutions and subsequent amino acid alterations. Notably, an RNA editing event at position A430 in petA introduced a premature stop codon, resulting in both truncated (15 kDa) and full-length (35 kDa) Cyt f isoforms. According to 3D protein calculation, these isoforms exhibited that the smaller size isoform may exhibit altered transmembrane protein stability, heme coordination, and electron transport efficiency. Structural modeling suggested that the truncated Cyt f had impaired redox activity. The reversion of specific petB edits (L150M, A154V) upon rehydration, alongside drought-triggered changes in electron transport linked to conserved editing patterns, establishes RNA editing as a dynamic, stress-responsive regulatory mechanism. Taken together, these findings reveal that RNA editing contributes to the functional plasticity of the Cyt b 6 f complex under drought by integrating protein isoform production, reversible amino acid changes, and metal homeostasis, ultimately supporting enhanced photosynthetic adaptation and drought tolerance in plants. • Photosynthetic optimization integrates RNA editing, protein turnover, and copper homeostasis in stress response. • RNA editing targets the b6f complex to balance electron flow, enhancing photosynthetic plasticity for drought resilience. • Partial RNA editing in petA results in a truncated Cyt f protein that reversibly downregulates electron flow. • Specific RNA edits (I132F, N134Y) reprogram Cyt f structure to fine-tune electron transport efficiency. • RNA editing in petB reversibly fine-tunes protein flexibility, enabling real-time photosynthetic stability during drought and recovery.