Low Doses of Anatase and Rutile Nanoparticles Differently Modulate Photosynthesis and Regulatory Genes: A Contribution to the Nanoagroindustry

Abstract

Industrial applications of titanium dioxide nanoparticles (TiO2 NPs) are wide, and their use in nano-fertilizing technology has been proposed in the last few years. Bioactivity evaluation of different TiO2 NPs formulations is therefore crucial, not only to select the most appropriate formulation but also to validate potential agro-applications. In the current work, we compared the bioactivity of the two most used TiO2 NPs formulations (anatase and rutile–anatase) on the photosynthesis of Lactuca sativa. Seeds were exposed to concentrations of 0, 10, and 50 mg L−1 of anatase (A) or rutile–anatase (RA). Germination rate was not affected by NPs, but root growth was stimulated mainly by RA50. Compared with control, RA showed positive effects on photophosphorylation-related parameters. A50 was more efficient in promoting the gas exchange phase (PN, Ci, gs, and E) and in stimulating the absorption of some nutrients. Expanding on the biochemical and physiological data, we show that RA50 stimulated several genes coding for proteins involved in the electron transport in thylakoids (psbA, petB, petA, psaA, psaC, ndhA, ndhD) and ATP synthesis (atpA, atpB). The transcript coding for the large subunit of RuBisCO (rbcL), was stimulated by lower concentration (RA10). This suggests that RuBisCO is highly sensitive to these NPs even at low doses. RA at low doses has been demonstrated to be the most promising NP. These discriminative effects of TiO2 NPs, based on their formulation and dose, may present advantages for their use in the precision nanoagroindustry.