ZmClpP6 modulates chloroplast development and photoprotection in maize

Proteostatic control of chloroplast biogenesis and homeostasis is crucial for photosynthetic efficiency. However, previous studies of this process have primarily focused on the model plant Arabidopsis and C3 crops, and its role in C4 species remains unexplored. The Clp protease complex, which is located in the stroma, plays a crucial role in proteostatic degradation. Mutations in the genes encoding this complex can result in embryonic and seedling lethality, stunted plant growth and development, and chlorosis. Here, we report that disruption of ZmClpP6 in maize results in transversely green and yellow striped leaves, with alternating green and yellow sectors forming during the night and day, respectively, and with yellow sectors especially prominent under high light conditions. High light treatment of mutants and wild-type maize leaves caused different changes in reactive oxygen species distribution and photosystem II stability, coinciding with progressive thylakoid membrane reorganization during leaf development. Intriguingly, the light-dependent alternating of transverse yellow-green crossbands diminished as leaves matured, suggesting compensatory regulation during developmental progression and phase transition. The zmclpP6 mutant phenotype is associated with altered accumulation of the photoprotective protein ZmELIP2 under high light, which interacts with the Clp protease complex and may be a potential degradation substrate. Our findings highlight the Clp protease as a key mediator of chloroplast plasticity in response to light. Functional analysis of the Clp protease complex in maize provides insights into how C4 plants balance photoprotection with chloroplast differentiation, offering a framework for understanding the integration of proteostatic control with environmental adaptation in crops.