Changes in the Ascorbate System during Seed Development of Vicia faba L.

Abstract

Large changes occur in the ascorbate system during the development of Vicia faba seed and these appear closely related to what are generally considered to be the three stages of embryogenesis. During the first stage, characterized by embryonic cells with high mitotic activity, the ascorbic acid/dehydroascorbic acid ratio is about 7, whereas in the following stage, characterized by rapid cell elongation (stage 2), it is lower than 1. The different ascorbic/dehydroascorbic ratio may be correlated with the level of ascorbate free radical reductase activity, which is high in stage 1 and lower in stage 2. Ascorbate peroxidase activity is high and remains constant throughout stages 1 and 2, but it decreases when the water content of the seed begins to decline (stage 3). In the dry seed, the enzyme disappears together with ascorbic acid. Ascorbate peroxidase activity is observed to be 10 times higher than that of catalase, suggesting that ascorbate peroxidase, rather than catalase, is utilized in scavenging the H(2)O(2) produced in the cell metabolism. There is no ascorbate oxidase in the seed of V. faba. V. faba seeds acquire the capability to synthesize ascorbic acid only after 30 days from anthesis, i.e. shortly before the onset of seed desiccation. This suggests that (a) the young seed is furnished with ascorbic acid by the parent plant throughout the period of intense growth, and (b) it is necessary for the seed to be endowed with the ascorbic acid biosynthetic system before entering the resting state so that the seed can promptly synthesize the ascorbic acid needed to reestablish metabolic activity when germination starts.

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.…”

“…As observed in this study (Fig. 1) a shift of the glutathione pool towards its oxidized form, GSSG, occurs in developing seeds to ensure the proper execution of the developmental pathway (Arrigoni et al 1992). The imposition of an oxidized environment, which can be achieved in culture through exogenous applications of the GSH-biosynthetic inhibitor BSO (GriYth and Meister 1979) (Fig.…”

Estudo enzimático da deterioração de sementes de Melanoxylon brauna submetidas ao envelhecimento natural e acelerado

“…As células são dotadas de mecanismos protetores de defesa contra EROs, prevenindo a sua formação e promovendo a remoção das formas reativas produzidas (Alscher et al, 2002), como pelos sistemas antioxidantes enzimáticos (Arrigoni et al, 1992;Chaitanya et al, 2000;Tommasi et al, 2001;Bailly, 2004). Vários trabalhos têm sido realizados na tentativa de explicar a relação entre o envelhecimento de sementes durante o armazenamento e a peroxidação de lipídios (Wilson Jr. e McDonald Jr., 1986;Kalpana e Madhava Rao, 1996;Camargo et al, 2000), com respostas variáveis, de acordo com a espécie.…”

Assessing wheat (Triticum aestivum L.) genetic diversity using quality traits, amplified fragment length polymorphisms, simple sequence repeats and proteome analysis

“…Among the AsA-glutathione cycle enzymes, DHAR had the highest increase in percentage during seed development (De Gara et al, 2003). Because there is shortage of AsA in seeds (Arrigoni et al, 1992), DHAR activity during early seed germination can protect the small AsA pool from oxidation (Pallanca & Smirnoff, 1999). It has also been suggested that the cold-regulated proteins are involved in the cryoprotection of the plasma membrane against freezing and dehydration-induced stress (Kreps et al, 2002;Garwe et al, 2003).…”