Functional and transcriptomic insights into plant response to arginine-functionalized nanohydroxyapatite treatment

The manipulation of the plant genome is essential for elucidating gene functions in plants and advancing the development of climate-resistant crops. We have demonstrated that a nanohydroxyapatite (nHA)-mediated gene delivery system is effective in the transformation of reporter genes into six plant species. Despite the potential advantages of nHA-mediated biomolecule delivery and its application as fertilizers, phytotoxicity concerns necessitate additional studies. While initial findings suggest the beneficial effects of nHA as a nanofertilizer at specific concentrations, a thorough investigation into its bioactivity is warranted. This study reports the bioactivity of nHA on two model plants, including a crop species, and examines the global gene expression alterations in Arabidopsis thaliana. Treatment of seeds and seedlings with arginine-functionalized nHA (R-nHA) at concentrations at 50, 200 and 500 µg/ml led to accelerated germination in Arabidopsis, an effect not observed in Nicotiana benthamiana. Additionally, R-nHA did not affect root growth in either model species but significantly promoted root and leaf growth in Triticum aestivum. Transcriptomic analysis revealed minimal transcriptional changes in Arabidopsis treated with R-nHA compared to a water control, including activated phytohormone signaling pathways and stress-responsive genes. Salicylic acid (SA) has been identified as a pivotal phytohormone in initiating stress resistance in response to R-nHA exposure in Arabidopsis, highlighting its essential role in plant defense mechanisms against both biotic and abiotic stresses. In summary, this study showed that R-nHA accelerates germination and promotes plant growth with minimal transcriptional changes, thereby laying the groundwork for the use of nHA in plant genome manipulations. This research indicates that nHAs are highly biocompatible for plant bionanotechnology applications.