Sucrose Regulates Elongation of Carrot Somatic Embryo Radicles as a Signal Molecule

Abstract

Elongation of carrot somatic embryo radicles was inhibited by sucrose at or above 5% (145 mM). This effect would not be released until the sucrose concentration was lowered again. Morphological and cytological studies as well as determination of ABA content and analysis of the expression mode of a Lea gene, all point to its similarity to natural dormancy and germination of seeds. Use of monosaccharides (glucose and fructose), other disaccharide (maltose), and isomolar concentration of osmotica (mannitol and sorbitol), did not show similar regulatory effect. It is thus clear that the regulatory effect is not a result of simple osmotic stress. Hexokinase inhibitors such as glucosamine and N -acetyl-glucosamine did not exert any influence on the regulation-deregulation effects of sucrose. Mannose, which inhibits germination of Arabidopsis seeds, did not prevent carrot somatic embryo radicles from elongating. It is thus inferred that this sucrose-signaling pathway may be independent of hexokinase. As a first step to understand the molecular mechanism of this process, a carrot sucrose transporter gene ( cSUT ) expressed in the embryos and roots specifically was isolated. Studies on transformed yeast mutant with cSUT cDNA identified its sucrose transport activity. Northern hybridization and gel retardation experiment revealed that there is a marked increase in expression of cSUT at the beginning of somatic embryo germination, and this is attributed to regulation on the level of transcription. This suggested the possibility that cSUT has an important role in this sucrose signal regulation system.

A Systematic Proteomic Study of Seed Filling in Soybean. Establishment of High-Resolution Two-Dimensional Reference Maps, Expression Profiles, and an Interactive Proteome Database

“…Interestingly, five Suc-binding proteins showed opposite expression trends, their relative abundance decreased during seed filling (spots 405, 463, 522, 631, and 754). The expression profiles of these proteins may support previous investigations on the importance of Suc as a signaling molecule in seed and embryo development (Konradova et al, 2002;Bate et al, 2004;Yang et al, 2004; for review, see Borisjuk et al, 2004).…”

The role of sucrose metabolizing proteins in hyperosmotic stress tolerance in sweet sorghum (Sorghum bicolor L. Moench)

“…The increase in SPS enzyme activity under stress was however not associated with sucrose content. Although sucrose synthase was favourable towards sucrose synthesis under stress, activity levels compared to SPS indicated that sucrose synthesis was solely dependent on the activity of SPS as previously reported in wheat stems at anthesis by Yang et al, (2004), and that this enzyme does not play a decisive role in regulating sucrose levels in sweet sorghum stems. Of the key sucrose metabolizing proteins investigated, invertases were significantly up-regulated by stress in both varieties, thus attributing to the observed hexose accumulation under stress.…”

Sugars induce anthocyanin accumulation and flavanone 3-hydroxylase expression in grape berries

“…In Arabidopsis, the sugar induction effect on anthocyanin accumulation is established via a sucrose specific pathway (Teng et al 2005;Solfanelli et al 2006), and the disaccharide analogs palatinose and turanose were used to illustrate the sucrose-specific signaling pathway in potato tubers and barley embryos (Yang et al 2004). But in our model, the sucrose-specific mechanism did not seem to be involved.…”