Abstract:

Salt stress causes seed vigor reduction and seed germination inhibition, which limits peanut production in Saline-alkali land. The metabolic process of seed germination plays an important role in seed germination and plant morphogenesis, which has gradually become an important indicator to evaluate seed vigor and quality. Having the peanut seed in different germination as study object, changes of basic nutrients and the differential metabolites along peanut seed germination under salt stress were analyzed by physiological indexes and liquid chromatography tandem-mass spectrometry（LC-MS/MS）. Seed germination after absorbing water prompted the catabolism of fats, proteins and soluble sugars. The levels of fats and soluble sugars decreased gradually with the germination time prolonging, while those of soluble protein first decreased and then increased. Principal component analysis（PCA）and partial least squares discriminant analysis（PLS-DA）showed that the metabolic profiles of those groups were different, indicating that salt stress largely impacted peanut seed metabolism. VIP analysis and KEGG pathway prediction analysis showed that there was little differentiated metabolites and none was enriched in any KEGG pathway during water absorption period, but they were enriched in 12 KEGG pathways during radicle elongation period under normal condition, indicating that the metabolism was more vigorous in the late germination period than in the early germination period. Salt stress dramatically increased levels of different metabolites, among which levels of osmotic protectors betaine and proline were significantly induced. In addition, differentiated metabolites significantly increased during water absorption period and radicle elongation period under salt stress, and they were enriched 26 and 31 KEGG pathways, respectively. Salt stress significantly promoted the related pathways such as energy metabolism, glycerophospholipid metabolism, glutathione metabolism, and glucosinolate biosynthesis, suggesting that may be associated with stress tolerance. Betaine and proline are likely two key metabolites, and glycerophospholipid metabolism, glutathione metabolism and glucosinolates biosynthesis may be important metabolic regulatory pathways for the adaptation to salt stress during germination. This study provides a theoretical basis and reference value for exploring new methods to promote peanut seed germination and emergence under salt stress and improving peanut germination rate in Saline-alkali land.

Key words: Arachis hypogaea, salt stress, germination, metabolomics, metabolic pathway