Characterized by a photocatalysis property, nanoanatase is closely related to the photosynthesis of spinach. It could not only improve light absorbance, transformation from light energy to electron energy, and active chemical energy, but also promote carbon dioxide (CO(2)) assimilation of spinach. However, the molecular mechanism of carbon reaction promoted by nanoanatase remains largely unclear. In this study, we report that the amounts of Rubisco activase (rca) mRNA in the nanoanatase-treated spinach were increased by about 51%, whereas bulk-TiO(2) treatment produced an increase of only 5%. Accordingly, the protein level of Rubisco activase from the nanoanatase-treated spinach was increased by 42% compared with the control; however, bulk-TiO(2) treatment resulted in a 5% improvement. Further analysis indicated that the activity of Rubisco activase in the nanoanatase-treated spinach was significantly higher than the control by up to 2.75 times, and bulk-TiO(2) treatment had no such significant effects. Together, one of the molecular mechanisms of carbon reaction promoted by nanoanatase is that the nanoanatase treatment results in the enhancement of rca mRNA expressions, protein levels, and activities of Rubisco activase, thereby leading to the improvement of Rubisco carboxylation and the high rate of photosynthetic carbon reaction.

Being a proven photocatalyst, nano-anatase is capable of undergoing electron transfer reactions under light. In previous studies, we had proven that nano-anatase improved photosynthesis and greatly promoted spinach growth. However, the molecular mechanisms of carbon reaction promoted by nano-anatase are still not clearly understood. In the present paper, reverse transcription polymerase chain reaction and Northern blotting were carried out, and the results showed that the expression of ribulose-1, 5-bisphosphate carboxylase/oxygenase (Rubisco) small subunit (rbcS) and Rubisco large subunit (rbcL) messenger RNA (mRNA) in the nano-anatase-treated spinach were obviously promoted, respectively, while the effects of bulk TiO2 were not so significant. Accordingly, the protein expression of Rubisco from the nano-anatase-treated spinach was increased by 40% compared with control. Further analysis indicated that the activity of Rubisco in the nano-anatase-treated spinach was significantly higher than the control, by up to 2.33 times, and bulk TiO2 treatment had no such significant effects. Together, one of the molecular mechanisms of carbon reaction promoted by nano-anatase is that the nano-anatase treatment results in the enhancement of Rubisco mRNA amounts, the protein levels, and activity of Rubisco, thereby leading to the improvement of Rubisco carboxylation and the high rate of photosynthetic carbon reaction.

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