Alterations of the glutathione redox state improve apical meristem structure and somatic embryo quality in white spruce (Picea glauca)

Abstract

In white spruce, an improvement of somatic embryo number and quality can be achieved through experimental manipulations of the endogenous levels of reduced (GSH) and oxidized (GSSG) glutathione. An optimal protocol for embryo production included an initial application of GSH in the maturation medium, followed by replacement with GSSG during the remaining maturation period. Under these conditions, the overall embryo population more than doubled, and the percentage of fully developed embryos increased from 22% to almost 70%. These embryos showed improved post-embryonic growth and conversion frequency. Structural studies revealed remarkable differences between embryo types, especially in storage product deposition pattern and organization of the shoot apical meristem (SAM). Compared with their control counterparts, glutathione-treated embryos accumulated a larger amount of starch during the early stages of development, and more protein and lipid bodies during the second half of development. Differences were also noted in the organization of SAMs. Shoot meristems of control embryos were poorly organized and were characterized by the presence of intercellular spaces, which caused separation of the subapical cells. Glutathione-treated embryos had well-organized meristems composed of tightly packed cells which lack large vacuoles. The improved organization of the shoot apical meristems in treated embryos was ascribed to a lower production of ethylene. Differences in meristem structure between control and treated embryos were also related to the localization pattern of HBK1, a shoot apical meristem 'molecular marker' gene with preferential expression to the meristematic cells of the shoot pole. Expression of this gene, which was localized to the apical cells in control embryos, was extended to the subapical cells of treated embryos. Overall, it appears that meristem integrity and embryo quality are under the direct control of the glutathione redox state.

A GlutathioneS-Transferase Regulated by Light and Hormones Participates in the Modulation of Arabidopsis Seedling Development

“…5B), which implies that AtGSTU17 can contribute to the regulation of the GSH/GSSG ratio; a high GSH/GSSG ratio is essential for cell division (Belmonte et al, 2005). However, AtGSTU17 in the dark may have a redundant effect with other GST members on GSH/GSSG ratio for hypocotyl elongation, which led to atgstu17 having a GSH/GSSG ratio similar to that of Col (Fig.…”

“…Bashandy et al (2010) reported that mutations of two key thiol reduction pathways, thioredoxin and GSH (the ntra ntrb cad2 mutant), resulted in a loss of auxin-regulated phenotypes such as apical dominance, vasculature, and secondary root production, and auxin transport and auxin levels, which implies that the GSH pool within cells is linked to auxin homeostasis. Moreover, alterations of the GSH redox state can improve apical meristem structure and somatic embryo quality in white spruce (Picea glauca; Belmonte et al, 2005). AtGSTU17, encoding a U class member of GST, has GST activity (Supplemental Fig.…”

“…S1), which indicates that AtGSTU17 may regulate GSH pools in Arabidopsis under light and various hormone conditions. The reduced (GSH) and oxidized forms (GSSG) of GSH, as well as its redox state, play critical roles in the control of plant development in response to changes in light and environmental signals (Loyall et al, 2000;Belmonte et al, 2005;Foyer and Noctor, 2009). To associate the GSH/GSSG ratio with the atgstu17 mutant phenotype under cFR light and auxin treatment, we determined the GSH/GSSG ratio in seedlings of atgstu17 (m1 and m2) and GSTU17OE (OE1 and OE2).…”

Different environmental conditions at initiation of radiata pine somatic embryogenesis determine the protein profile of somatic embryos

“…The generation of hydrogen peroxide and its regulation by the activation of antioxidant enzymes have been recorded at the beginning of SE formation (Lilik et al 2005;Ma et al 2012a, b). It was also shown that the redox state of the culture medium had an important effect on Norway spruce embryo yield and quality (Belmonte et al 2005). Based in these observations we can discuss that the presence of OsmC protein in somatic embryos initiated at high temperature could be helpful for cell development of a redox homeostasis system and maintenance of cell differentiation.…”

Characterization of the antioxidant system during the vegetative development of pea plants

“…The GSH/GSSG ratio clearly influences the cell-cycle progression. A high GSH/GSSG ratio is essential for cell division and proliferation during the initial stages of embryo development, but later in development the redox status of the glutathione pool decreases (Belmonte et al 2005). Studies using a GSH-deficient mutant or L-butathione-[S,R]-sulfoximine (BSO; an inhibitor of GSH biosynthesis) treatments suggest that GSH plays a key role in promoting signals which permit cell-cycle progression in roots and hence root growth (Vernoux et al 2000, Maughan andFoyer 2006).…”