PeGLK1-1 Enhances Photosynthesis by Promoting Carbon Fixation Capacity of the Calvin Cycle in Bamboo.

The greenhouse effect, primarily driven by CO2 is changing the global climate and threatening ecosystem and human sustainability. Bamboo plays an integral role in mitigating climate change with its excellent photosynthetic carbon fixation capacity. The Golden2-like (GLK) transcription factor is a critical regulator of photosynthesis. In this study, we identified four GLK members in moso bamboo (Phyllostachys edulis), among which PeGLK1-1 functioned as a principal regulator of photosynthesis. Overexpressing PeGLK1-1 significantly enhanced the carbon fixation capacity of transgenic rice under elevated CO2 (eCO2) environment. Moreover, PeGLK1-1 was positively correlated with most photosynthesis-related genes, such as PeRbcS2 and PePRK1 in the Calvin cycle. PeGLK1-1 bound to 5'-AAAAA-3' in the promoters of PeRbcS2 and PePRK1, thereby activating their transcription. Furthermore, overexpressing PeRbcS2 and PePRK1 enhanced the photosynthetic capacity of transgenic rice under eCO2 environment. In planta gene editing of PeRbcS2 and PePRK1 led to a decrease in photosynthetic capacity, whereas transient overexpression of them exhibited opposite trends. Collectively, eCO2 environment could induce the expression of PeGLK1-1 to activate the Calvin cycle genes, ultimately enhancing the carbon fixation capacity. This study provides crucial evidence for GLK regulating the Calvin cycle, which will contribute to breeding new bamboo varieties with efficient carbon fixation capacity.