Proteomics Analysis Reveals Non-Controlled Activation of Photosynthesis and Protein Synthesis in a Rice Mutant under High Temperature and Elevated CO₂ Conditions.

Rice nucleotide pyrophosphatase/phosphodiesterase 1 (NPP1) catalyzes the hydrolytic breakdown of the pyrophosphate and phosphodiester bonds of a number of nucleotides including ADP-glucose and ATP. Under high temperature and elevated CO₂ conditions (HT + ECO₂), the knockout rice mutant displayed rapid growth and high starch content phenotypes, indicating that exerts a negative effect on starch accumulation and growth. To gain further insight into the mechanisms involved in the downregulation induced starch overaccumulation, in this study we conducted photosynthesis, leaf proteomic, and chloroplast phosphoproteomic analyses of wild-type (WT) and plants cultured under HT + ECO₂. Photosynthesis in leaves was significantly higher than in WT. Additionally, leaves accumulated higher levels of sucrose than WT. The proteomic analyses revealed upregulation of proteins related to carbohydrate metabolism and the protein synthesis system in plants. Further, our data indicate the induction of 14-3-3 proteins in plants. Our finding demonstrates a higher level of protein phosphorylation in chloroplasts, which may play an important role in carbohydrate accumulation. Together, these results offer novel targets and provide additional insights into carbohydrate metabolism regulation under ambient and adverse conditions.