Nanoceria seed priming enhanced salt tolerance in rapeseed through modulating ROS homeostasis and α-amylase activities

Abstract

Background Salinity is a big threat to agriculture by limiting crop production. Nanopriming (seed priming with nanomaterials) is an emerged approach to improve plant stress tolerance; however, our knowledge about the underlying mechanisms is limited. Results Herein, we used cerium oxide nanoparticles (nanoceria) to prime rapeseeds and investigated the possible mechanisms behind nanoceria improved rapeseed salt tolerance. We synthesized and characterized polyacrylic acid coated nanoceria (PNC, 8.5 ± 0.2 nm, −43.3 ± 6.3 mV) and monitored its distribution in different tissues of the seed during the imbibition period (1, 3, 8 h priming). Our results showed that compared with the no nanoparticle control, PNC nanopriming improved germination rate (12%) and biomass (41%) in rapeseeds (Brassica napus) under salt stress (200 mM NaCl). During the priming hours, PNC were located mostly in the seed coat, nevertheless the intensity of PNC in cotyledon and radicle was increased alongside with the increase of priming hours. During the priming hours, the amount of the absorbed water (52%, 14%, 12% increase at 1, 3, 8 h priming, respectively) and the activities of α-amylase were significantly higher (175%, 309%, 295% increase at 1, 3, 8 h priming, respectively) in PNC treatment than the control. PNC primed rapeseeds showed significantly lower content of MDA, H2O2, and •O2− in both shoot and root than the control under salt stress. Also, under salt stress, PNC nanopriming enabled significantly higher K+ retention (29%) and significantly lower Na+ accumulation (18.5%) and Na+/K+ ratio (37%) than the control. Conclusions Our results suggested that besides the more absorbed water and higher α-amylase activities, PNC nanopriming improves salt tolerance in rapeseeds through alleviating oxidative damage and maintaining Na+/K+ ratio. It adds more knowledge regarding the mechanisms underlying nanopriming improved plant salt tolerance. Graphical abstract

Plant Salinity Stress Response and Nano-Enabled Plant Salt Tolerance

“…For example, nanozyme poly(acrylic) acid-coated cerium oxide nanoparticles (PNC) can improve salinity stress tolerance of cotton mainly by alleviating ROS accumulation in seedling roots ( An et al, 2020 ). Similar results were also found in wheat ( Mushtaq et al, 2017 ), tomato ( Faizan et al, 2021 ), soybean ( Farhangi-Abriz and Torabian, 2018 ), and rapeseed ( Khan et al, 2021 ). Carbon quantum dots can significantly improve the activity of antioxidant enzyme system to reduce the content of ROS and to alleviate oxidative damage on cell membrane, thus enhancing grape salt tolerance ( Gohari et al, 2021 ).…”

“…For example, multi-walled carbon nanotubes (MWCNTs), cerium oxide nanoparticles, and zinc oxide nanoparticles (SeNPs and ZnONPs) can significantly alleviate the inhibition of salt stress on the growth of rapeseed seedlings. Seed priming using cerium oxide nanoparticles, SeNPs and ZnONPs, also significantly improves the germination rate of rapeseed seeds under salt stress ( Rossi et al, 2017 ; Zhao et al, 2019 ; El-Badri et al, 2021 ; Khan et al, 2021 ; Li et al, 2022 ). For more details, please refer to Table 1 .…”

“…Nanoceria are known as nanozyme and potent catalytic ROS (reactive oxygen species) scavenger, having a large number of surface oxygen vacancies which can convert ROS, i.e., H 2 O 2 , O 2 − , and • OH to its non-radical counterparts. To date, the mechanisms behind nanoceria improved plant salt tolerance ( Figure 2 ) are: (1) maintaining ROS homeostasis via direct scavenging of ROS or modulating antioxidant system ( Rossi et al, 2017 ; Wu et al, 2018c ), (2) improving mesophyll cells’ ability to retain K + ( Wu et al, 2018d ), (3) improving shoot Na + exclusion ability to avoid over-accumulation of Na + in leaf ( Liu et al, 2021a ), (4) improving the production of gas signaling molecules, i.e., NO (nitric oxide; Zhou et al, 2021 ), (5) increasing α-amylase activities to improving seed germination ( Khan et al, 2021 ), (6) decreasing lipoxygenase activities to reduce membrane oxidative damage ( Li et al, 2022 ES Nano), and (7) allowing Na + being transported to shoot via shortening root apoplastic barriers ( Rossi et al, 2017 ). Some of these mechanisms might be shared between different nanomaterials in terms of improving plant salt tolerance.…”

Exogenous SA Affects Rice Seed Germination under Salt Stress by Regulating Na+/K+ Balance and Endogenous GAs and ABA Homeostasis

“…ROS accumulation is commonly observed during seed imbibition [ 47 ]. Luo et al [ 45 ] demonstrated that salinity-induced ROS accumulation inhibited seed germination.…”

“…Superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) are the key enzymes involved in the metabolism of ROS. An increase in their activities contributes to the removal of ROS [ 47 ].…”