**9. Reserve mobilization**

Recent transcriptome and proteome study of cabbage (*Brassica oleracea*) and *Arabidopsis* seeds as well as integrated transcriptomic and proteomic approach in study of rapeseeds (*Brassica napus*) osmopriming revealed that germination and priming altered similar processes [36, 136, 138]. Indeed, it is proposed that germination-related processes such as respiration, energy metabolism, and early reserve mobilization can also occur during priming [16] (**Figure 2**). Faster and uniform rice (*Oryza sativa*) seed germination due to priming was related to im‐ proved activity of α-amylase, resulting in increased level of soluble sugars in primed kernels [168]. Sung and Chang [169] have shown that priming of maize (*Zea mays*) seeds leads to increased activity of enzymes for carbohydrates (α and β amylases) and lipids (isocitrate lyase, ICL) mobilization. Priming of chickpea (*Cicer arietinum* L. Cv PBG-1) seeds with mannitol led to increased activity of amylase, invertases (acid and alkaline), sucrose synthase (SS), and sucrose phosphate synthase (SPS) in shoots of primed seedlings. The higher amylase activity in shoots suggests a rapid hydrolysis of transitory starch formed in the shoots of primed seedlings leading to more availability of glucose for seedling growth. [170]. Higher content of soluble protein, aldolase, and ICL activity has been observed in haloprimed pepper (*Capsicum annum* L) seeds than in control seeds [171]. Moreover, the α-glucosidase accumulation and increased level of globulin degradation products were observed during the priming process of sugar beet (*Beta vulgaris* L.) seed [172]. Similar observation on primed sugar beet seed has been done by Capron et al. [173] who showed increased solubilization of 11S-globulin-βsubunit in response to hydro- and osmopriming. Gallardo et al. [136] have also observed higher polypeptides content in both hydro- and osmoprimed *Arabidopsis* seeds. They were identified as products of 12S-cruciferin-β-subunit degradation.

varieties (MSk326 and HHDJY) was due to increased activity of antioxidant enzymes (SOD, POD, CAT, and APX) as a result of priming seeds with putrescine [165]. Results obtained by Islam et al. [167] showed that in haloprimed wheat (*Triticum aestivum*) seeds, increased activity of CAT, POD, and APX enhanced tolerance to salinity stress. Osmopriming with PEG has improved sorghum (*Sorghum bicolor*) seed germination and seedling establishment under adverse soil moisture conditions and has been correlated with antioxidant system activation (APX, CAT, POD, and SOD) [3]. Rice (*Oryza sativa*) seeds primed with polyethylene glycol (PEG) showed increased activity of APX in parallel with decreased activity of SOD, POD, and CAT under ZnO nanoparticles stress [38]. The same authors have also observed downregulation of genes encoding the antioxidant enzymes (*APXa, APXb, CATa, CATb, CATc, SOD2*, and *SOD3*) in PEG primed seeds under nano-ZnO stress. They have concluded that priming with PEG significantly alleviates the toxic effects of nano-ZnO through improved cell

22 New Challenges in Seed Biology - Basic and Translational Research Driving Seed Technology

Seed aging during storage is associated with ROS production. Appearance of oxidative stress results in a decrease of seed quality. Kibinza et al. [161] showed that priming plays an important role in seed recovery from aging through CAT activation. Their results revealed accumulation of hydrogen peroxide (H2O2) and reduction of CAT at the gene expression level and protein content during sunflower (*Helianthus annuus* L) seed aging. Interestingly, the adverse results of aging were recovered by seed osmopriming, which led to induction of CAT synthesis by

Summing up, the management of oxidative status in primed seeds plays a very important role as a machinery, which leads to protection against oxidative stress, recovery from aging, and regulation of ROS production/accumulation. Alleviation in ROS level exerts a signal, which could be perceived, transduced, and crosstalk with other signaling pathways, thus executing

Recent transcriptome and proteome study of cabbage (*Brassica oleracea*) and *Arabidopsis* seeds as well as integrated transcriptomic and proteomic approach in study of rapeseeds (*Brassica napus*) osmopriming revealed that germination and priming altered similar processes [36, 136, 138]. Indeed, it is proposed that germination-related processes such as respiration, energy metabolism, and early reserve mobilization can also occur during priming [16] (**Figure 2**). Faster and uniform rice (*Oryza sativa*) seed germination due to priming was related to im‐ proved activity of α-amylase, resulting in increased level of soluble sugars in primed kernels [168]. Sung and Chang [169] have shown that priming of maize (*Zea mays*) seeds leads to increased activity of enzymes for carbohydrates (α and β amylases) and lipids (isocitrate lyase, ICL) mobilization. Priming of chickpea (*Cicer arietinum* L. Cv PBG-1) seeds with mannitol led to increased activity of amylase, invertases (acid and alkaline), sucrose synthase (SS), and sucrose phosphate synthase (SPS) in shoots of primed seedlings. The higher amylase activity in shoots suggests a rapid hydrolysis of transitory starch formed in the shoots of primed

structures of leaf and roots.

**9. Reserve mobilization**

activating gene expression and translation of the enzyme.

physiological response by activation or repression of molecular processes.

Kubala et al. [36] have shown that during *Brassica napus* seeds osmopriming and post-priming germination accumulation of transcript and proteins for seed storage proteins occurred. The authors have observed up-accumulation of cruciferin CRU1. The group of six genes encoding GDSL-like lipases, playing a role in triacylglycerols (major storage lipids in rape seeds) catabolism, were strongly up-regulated during post-priming germination while the other three genes for GDSL-like lipases as well as extracellular lipase 6 were up-regulated in osmoprimed seeds [36]. The activation of lipid catabolism-related genes was correlated with the activation of genes involved in lipid transport such as genes encoding bifunctional inhibitor/lipidtransfer protein/seed storage 2S albumin superfamily protein [36]. Priming can also reduce a level of oleosins-proteins, which surround oil bodies. In osmoprimed *Brassica napus* seeds as well as during post-priming germination, down accumulation of oleosin S4-3 protein and down-regulation of *OLEOSIN2* gene were observed, respectively [36].

Activation of respiration and rapid ATP production is primary metabolic events occurring during priming [18], and higher respiratory activity is required to cover energy pool for speed up germination. The increased ATP level/energy charge after priming was observed in tomato (*Solanum lycopersicum*), eggplant (*Solanum melongena*), araucaria (*Araucaria columnaris*), spinach, oat (*Avena sativa*), and cabbage (*Brassica oleracea*) [174, 175]. Primed seed needs a large amount of fuel, which supplies energy required for higher reserve mobilization rate. All together lead to improved energy turnover and increased metabolism rate of primed seed and contribute to better germination and stress tolerance.
