| An efficient and sustainable agricultural system is vital to the existence of humanity.Although current agricultural practices can meet the food needs of eight billion people,the ever-increasing population and environmental changes will inevitably place higher requirements on the quantity and quality of food production.To meet production needs and cope with environmental changes,a new agricultural technology revolution is booming.Nowadays,nanotechnology has become a promising tool,which can create smarter and more efficient food production mothods for modern agriculture practices.The latest progress of nanotechnology in agricultural field mainly includes four aspects:nanofertilizers,nanopesticides,nanobiosensors and nano-based remediation.The use of nanofertilizers is one of the main factors to increase crop yields.According to reports,many nanomaterials(for example,carbon-based nanomaterials,metal and metal oxide nanomaterials)can effectively transport nutrients and improve crop yield and quality.However,the accumulation,migration and transformation of nanomaterials in plants and their enrichment in the food chain have aroused attention to the safety of nanomaterials.Selenium(Se)is essential for life and has attracted growing interest in both human health and agricultural field of science.It is reported that the range between beneficial concentration and toxic concentration of Se is relatively narrow.Low Se concentration can promote plant growth,increase yield,resist oxidative stress and pathogen infection,and improve nutritional quality of plants,while high Se concentrations is toxic,limiting plant growth and development.When different forms of Se enter plant cells,they can enter sulfur transport pathways and form selenoamino acids,such as selenocysteine(SeCys)and selenomethionine(SeMet).Compared with inorganic Se,nano-Se has low toxicity,excellent dispersibility and antibacterial ability,and can rapidly increase Se content in crops in a short period of time.Although the bioavailability of different forms of Se has been reported,but the regulation effects and mechanisms of Se on plants is still unclear.In this study,we systematically studied the effects,absorption,transformation and regulation mechanisms of selenium nanoparticles on Arabidopsis thaliala,a model plant.The main research results were summarized as follows:(1)Amorphous selenium nanoparticles(SeNPs)were synthesized in the laboratory through chemical reduction.The particle size distribution was uniform and stable,and the particles were spherical,with an average particle size of 59 nm in deionized water.In 1/2 MS media,the root length of Arabidopsis was promoted under low concentration but inhibited under high concentration when exposed to different concentrations of SeNPs(0,0.5,1,3,5,7,10,15 mg/kg)for 10 days.In soil,the fresh weight(stem,leaf)and siliques number of Arabidopsis showed the same trend after 28 days of exposure to different concentrations of SeNPs(0,2,5,10,20,50,100,225,450 μg/plant).(2)Based on transcriptomics analysis of key differential genes and GO functional cluster analysis,we found that low-concentration SeNPs(1 mg/kg)treatments promoted the growth of protocambium,xylem,and phloem tissues of Arabidopsis roots,and then promoted the geotropic growth of roots.Meanwhile,SeNPs promoted glycolysis of leaves,stimulated the expression of genes related to growth and nutrient storage(VSP1,AT2G16660),and then promoted growth and starch accumulation.In addition,the exposure of high-concentration SeNPs(15 mg/kg)caused plant stress response,including oxidative stress(such as increased reactive oxygen species(ROS)levels and upregulation of antioxidant enzyme-related gene expression),and up-regulation of protective proteins(such as heat shock protein).Meanwhile,affected carbon allocation,and resulting in an increase of sucrose content and a decrease of starch content in leaves.Meanwhile,H2O2 and O2-levels were analysed by staining roots of Arabidopsis.Compared with the control,H2O2 was eliminated under low-concentration SeNPs(1 mg/kg)treatment but accumulated in the root tips and maturation zone at highconcentration SeNPs(15 mg/kg)exposure.(3)Se can be transported from exposed leaves to other compartments of Arabidopsis by detecting Se content in different parts.In addition,the surfactant Silwet L-77 significantly promoted the uptake and transportation of SeNPs.Using high performance liquid chromatography-inductively coupled plasma mass spectrometry(HPLC-ICP-MS)to analyze the Se species in plant samples,we found that SeNPs mainly converted to organic Se in Arabidopsis,and the content of SeMet is the highest.At the same time,we detected an unknown selenide in leaves exposed to low levels of SeNPs(1 mg/kg),and the original SeCys peak of standard showed double peaks in the root samples,which was speculated to be a chiral substance of SeCys.These substances needed to be verified and analyzed.Therefore,futher research in this area will be the focus of future work.Our research results directly proved the absorption,accumulation and transformation of SeNPs in plants,which not only deepened the understanding of ecological safety of SeNPs,but also provided theoretical support for the security application of nanofertilizers in agricultural production. |
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