A comparative study of glutathione and ascorbate metabolism during germination of Pinus pinea L. seeds

Abstract

The ascorbate and glutathione systems have been studied during the first stages of germination in orthodox seeds of the gymnosperm Pinus pinea L. (pine). The results indicate that remarkable changes in the content and redox balance of these metabolites occur in both the embryo and endosperm; even if with different patterns for the two redox pairs. Dry seeds are devoid of the ascorbate reduced form (ASC) and contain only dehydroascorbic acid (DHA). By contrast, glutathione is present both in the reduced (GSH) and in the oxidized (GSSG) forms. During imbibition the increase in ASC seems to be mainly caused by the reactivation of its biosynthesis. On the other hand, the GSH rise occurring during the first 24 h seems to be largely due to GSSG reduction, even if GSH biosynthesis is still active in the seeds. The enzymes of the ascorbate--glutathione cycle also change during germination, but in different ways. ASC peroxidase (EC 1.11.1.11) and glutathione reductase (EC 1.6.4.2) activities progressively rise both in the embryo and in endosperm. These changes are probably required for counteracting production of reactive oxygen species caused by recovery of oxidative metabolism. The two enzymes involved in the ascorbate recycling, ascorbate free radical (AFR) reductase (EC 1.6.5.4) and DHA reductase (EC 1.8.5.1), show different behaviour: the DHA reductase activity decreases, while that of AFR reductase remains unchanged. The relationship between ascorbate and glutathione metabolism and their relevance in the germination of orthodox seeds are also discussed.

Buthionine sulfoximine (BSO)-mediated improvement in cultured embryo quality in vitro entails changes in ascorbate metabolism, meristem development and embryo maturation

“…The glutathione redox state, established by the endogenous balance of GSH and GSSG, plays a key role in a variety of developmental processes (Tommasi et al 2001;Yeung et al 2005), including embryogenesis (Arrigoni et al 1992;Belmonte et al 2006;. As observed in this study (Fig.…”

Changes in the reduction state of ascorbate and glutathione, protein oxidation and hydrolysis leading to the development of dehydration intolerance in Triticum aestivum L. seedlings

“…GSSG) content is higher in tolerant seedlings than sensitive seedlings. The lowered level of GSH with germination confirms the previous report for higher plants (Tommasi et al 2001). The rise in activities of ascorbate peroxidase and glutathione reductase (GR) with seedling age suggest the increased utilization of AsA and GSH with the progression of germination.…”

Allelochemical ethyl 2-methyl acetoacetate (EMA) induces oxidative damage and antioxidant responses in Phaeodactylum tricornutum

“…GST is an important enzyme to transform harmful substances from environment [16,17]. Non-enzymatic antioxidant system includes GSH system and AsA system, which is another important cellular defense system to remove environmental oxidative stress [18][19][20]. The relationship between enzymes and non-enzymatic antioxidants is very complicated.…”