Rubisco activase (RCA) plays a pivotal role in plant drought stress responses by regulating Rubisco activity to maintain photosynthetic efficiency, thereby enhancing plant adaptability to water-deficient environments. In this study, we generated RCA-overexpressing maize lines (OE) to investigate the RCA functional mechanism under drought stress. During drought treatment, OE materials exhibited markedly enhanced drought tolerance compared to wild-type (WT) counterparts, as evidenced by the restoration of plant condition and vitality after rehydration. Energy conversion analyses revealed that drought stress suppressed both PSI and PSII, while OE lines demonstrated a greater adaptive capacity in mitigating these declines. Progressive drought exposure induced slower and less pronounced reductions in chlorophyll a fluorescence transient (OJIP), 820 nm modulated reflectance (MR), and delayed chlorophyll a fluorescence (DF) in OE plants relative to WT. These findings demonstrate that RCA overexpression alleviates drought-induced impairments in linear electron flow, reduces oxidative damage to PSI reaction centers and plastoquinone pools, and preserves electron transport integrity at the PSI acceptor side. Collectively, our results demonstrate that RCA overexpression enhances drought tolerance in maize at the seedling stage by safeguarding the operational integrity of the photosynthetic electron transport system under water deficit.
Wu et al. (Sat,) studied this question.