New evidence for a role for thioredoxin h in germination and seedling development

Abstract

Abstract. Thioredoxin of the h-type earlier linked to the reduction of wheat (Triticum durum Desf. cv. Monroe) endosperm proteins -was converted from an oxidized to a partially reduced state during germination and seedling development. While the abundance of thioredoxin progressively decreased during this period, the availability of reducing equivalents, defined as the product of the relative abundance of thioredoxin and the percent reduction, increased. The amount of the enzyme catalyzing the reduction of thioredoxin h (NADP-thioredoxin reductase) remained constant. The activities of enzymes generating the NADPH needed for the reduction of thioredoxin (glucose 6-phosphate and 6-phosphogluconate dehydrogenases) increased. The level of thioredoxin h in the endosperm appeared to be controlled by the embryo via hormones. Gibberellic acid enhanced the disappearance of thioredoxin, whereas abscisic acid showed the opposite effect. Moreover, uniconazole, an inhibitor of gibberellic acid synthesis, slowed seedling growth and inhibited the disappearance of thioredoxin in a manner reversible by gibberellic acid. The results are consistent with a role for thioredoxin h in initiating the mobilization of nitrogen and carbon needed for germination and seedling development.

Role of H2O2in pea seed germination

“…15 Alternatively, H 2 O 2 could act, directly or indirectly impairing the ABA transport from the cotyledon to the embryo inducing a decrease in ABA, stimulating the germination process. 13 Finally, the decrease in ABA could induce a MAPK-mediated decrease in the ethylene precursor 1-aminocyclopropane carboxylic acid, favoring epicotyl and radicle emergence by H 2 O 2 treatment.…”

Thioredoxins: structure and function in plant cells

“…Based on biochemical reactivity, many roles have been proposed for thioredoxin h in plants. Several papers indicate that it is involved in grain reserve mobilization processes through the destabilization of trypsin inhibitor proteins and activation of a recently discovered calcium-dependent, thiol-regulated protease called thiocalsin (Jiao et al, 1992;Shin et al, 1993;Besse et al, 1996;Lozano et al, 1996). On the other hand, no clear functions have been proposed for thioredoxin h in leaves so far.…”

Cadmium affects the NADP-thioredoxin reductase/thioredoxin system in germinating pea seeds

“…Subsequent events, including the mobilization of the major reserves, are associated with the growth of the seedling (Bewley 1997). A potential role of Trxs in redox status of storage proteins and proteolysis during germination has been already suggested (Lozano et al 1996;Montrichard et al 2003;Alkhalfioui et al 2007). They appear to play a role in the reduction of critical disulfide bonds of proteins (Kobrehel et al 1992;Besse et al 1996;Lozano et al 1996;Schu¨rmann and Jacquot 2000).…”

“…They appear to play a role in the reduction of critical disulfide bonds of proteins (Kobrehel et al 1992;Besse et al 1996;Lozano et al 1996;Schu¨rmann and Jacquot 2000). For example; Trx h acts as an early wake-up call in seed germination, facilitating the freeing of nitrogen and carbon through the activation of proteases and the inactivation of proteinaceous inhibitors (Besse et al 1996;Lozano et al 1996).…”