Seed priming with polyethylene glycol regulating the physiological and molecular mechanism in rice (Oryza sativa L.) under nano-ZnO stress

Abstract

The present study was designed to highlight the impact of seed priming with polyethylene glycol on physiological and molecular mechanism of two cultivars of Oryza sativa L. under different levels of zinc oxide nanorods (0, 250, 500 and 750 mg L −1). Plant growth parameters were significantly increased in seed priming with 30% PEG under nano-ZnO stress in both cultivars. Whereas, this increase was more prominent in cultivar Qian You No. 1 as compared to cultivar Zhu Liang You 06. Significant increase in photosynthetic pigment with PEG priming under stress. Antioxidant enzymes activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) as well as malondialdehyde (MDA) contents were significantly reduced with PEG priming under nano-ZnO stress. Gene expression analysis also suggested that expression of APXa, APXb, CATa, CATb, CATc, SOD1, SOD2 and SOD3 genes were down regulated with PEG priming as compared to non-primed seeds under stress. The ultrastructural analysis showed that leaf mesophyll and root cells were significantly damaged under nano-ZnO stress in both cultivars but the damage was prominent in Zhu Liang You 06. However, seed priming with PEG significantly alleviate the toxic effects of nano-ZnO stress and improved the cell structures of leaf and roots in both cultivars.Plants exposed to high concentrations of heavy metals experience changes in physiological, biochemical and molecular mechanisms of plant cells 1 . Uptake of nanoparticles (NPs) through primary roots is usually barred due to presence of suberinized exo-and endodermis. However, lateral root junctions are the primary sites through which NPs could enter the xylem via cortex and the central cylinder 2 . The higher concentrations of titanium dioxide (TiO 2 ) enhanced the alterations in mitotic activity and chromosomal aberrations, indicating genotoxic effects of nanoparticles (NPs) 3 . Nano-ZnO stress shows more detrimental effects on germination and root growth of rice as compared to TiO 2 nanoparticles 4 . Recently, Ng et al. studied the molecular downstream effects of ZnO nanoparticles on p53 signaling pathways, suggesting that ZnO nanoparticles might be sufficiently genotoxic to stimulate the DNA damage machinery and it might have caused DNA lesions because p53 was upregulated and phosphorylated with a concomitant decrease in cell cycle progression after seven days 5 . Furthermore, Giovanni et al. found that noncytotoxic zinc oxide NPs level (10 mg/L) could elevate the intracellular oxidative stress 6 . It has been observed that

Limitation of Improvement in Germination by Osmopriming of Differentially Aged Non-Orthodox Neem (Azadirachta indica) Seeds

“…The results of this study indicate that osmopriming of aged seeds has significant positive effect on the germination and seed vigour. Similar results, i.e., priming induced improvement in seed germination have been reported earlier [8,[25][26][27][28]. However, our data indicates that 12-17% improvement occurs in primed seed compared to aged seeds; such improvement only limited up to 50% germination level of ageing (Table 1).…”

Hydropriming and Biopriming Improve Medicago truncatula Seed Germination and Upregulate DNA Repair and Antioxidant Genes

“…The SOD enzyme catalyzes the dismutation of superoxide anion to hydrogen peroxide (H 2 O 2 ), while APX plays a key role catalyzing the conversion of H 2 O 2 into water, using ascorbate as a specific electron donor [52,53]. Enhanced accumulation of antioxidant enzymes following different seed priming methods (e.g., osmopriming, halopriming, hormopriming) has been previously reported in a number of plant species (Moringa oleifera [54], Vigna radiata [55], Triticum aestivum [56], Oryza sativa [57], Sorghum bicolor [58], Brassica napus [59]), and these were even correlated with changes in gene expression patterns [58,59]. Another group of interesting ROS scavengers includes metallothioneins (MTs), small cysteine-rich proteins that accumulate in response to toxic levels of heavy metals [60].…”

The Integration of Bio and Organic Fertilizers Improve Plant Growth, Grain Yield, Quality and Metabolism of Hybrid Maize (Zea mays L.)

“…Seed priming has been frequently used to improve seed germination and seedling development and can also improve plant growth in a wide range of environmental conditions [30][31][32][33][34][35]. As a priming agent, humic acid (HA) are usually used as a kind of hormone that promotes plant growth rather than improving the chemical or the physical conditions of the soil.…”