[Effect of oligosaccharides on adaptation of winter wheat seedlings to negative temperature]. / Uchastie oligosakharidov v adaptatsii prorostkov ozimoi pshenitsy k otritsatel'noi temperature.

We studied the dynamics of endogenous content of bioactive oligosaccharides in the roots of winter wheat seedlings. Previously these oligosaccharides proved to mediate development of frost resistance during the first days of hardening (Zabotina et al., 1998). The changes in their endogenous content can be described by a single-humped curve peaking 6 h after the onset of frost hardening. The capacity of these polysaccharides to increase frost resistance (LT50 was evaluated by leakage of electrolytes) when added to growth medium did not depend on the pretreatment duration (from 1.5 to 18 h) but decreased if they were introduced in the course of the adaptive response. Inhibition of the adaptive response by inhibitors of RNA and protein synthesis was ceased in the presence of the oligosaccharides. We believe that the oligosaccharides that are products of metabolism of the cell wall polysaccharides are involved in adaptation to low temperature.

Biologically active oligosaccharides from pectins of Pisum sativum L. seedlings affecting root generation.

Two physiologically active oligosaccharide fractions were isolated from pectin of Pisum sativum L. cell wall after its partial acid hydrolysis. These fractions displayed stimulating and inhibiting effects on root formation in thin-layer explants. The subsequent separation of these fractions by gel permeation and anion-exchange chromatography resulted in fractions with effective concentrations two orders of magnitude lower than the concentrations of the initial fractions. The resulting oligosaccharides displayed their effect on the earliest stage of the rhizogenesis associated with formation of root primordias. The rhizogenesis-inhibiting fraction suppressed cell division by 30-50%. The stimulating fraction mainly contained fragments of xyloglucan and galactan, and the inhibiting fraction contained fragments of xyloglucan, galactan, and arabinan. The polymerization degrees of the stimulating and of the inhibiting oligosaccharides were 10-11 and 5-6, respectively.

Synthesis and Turnover of Cell-Wall Polysaccharides and Starch in Photosynthetic Soybean Suspension Cultures.

Soybean (Glycine max [L.] Merr.) suspension cultures grown under photoautotrophic and photomixotrophic (1% sucrose) culture conditions were used in 14CO2 pulse-chase experiments to follow cell-wall polysaccharide and starch biosynthesis and turnover. Following a 30-min pulse with 14CO2, about one-fourth of the 14C of the photoautotrophic cells was incorporated into the cell wall; this increased to about 80% during a 96-h chase in unlabeled CO2. Cells early in the cell culture cycle (3 d) incorporated more 14C per sample and also exhibited greater turnover of the pectin and hemicellulose fractions as shown by loss of 14C during the 96-h chase than did 10- and 16-d cells. When the chase occurred in the dark, less 14C was incorporated into the cell wall because of the cessation of growth and higher respiratory loss. The dark effect was much less pronounced with the photomixotrophic cells. Even though the cell starch levels were much lower than in leaves, high 14C incorporation was found during the pulse, especially in older cells. The label was largely lost during the chase, indicating that starch is involved in the short-term storage of photosynthate. Thus, these easily labeled and manipulated photosynthetic cells demonstrated extensive turnover of the cell-wall pectin and hemicellulose fractions and starch during the normal growth process.

Biologically-active soluble oligosaccharides from pea stem tissues.

Two active fractions of soluble oligosaccharides were isolated from pea (Pisum sativum L.) stem tissues. Both fractions are capable of affecting different phases of root development on buckwheat thin cell-layer explants (TCLs) and of inhibiting auxin-promoted growth of etiolated pea stem segments. The existence of non-wall bioactive oligosaccharides which may have a role in cell development in vivo is proposed.

Stimulation of root development on buckwheat thin cell-layer explants by pectic fragments from pea stem cell walls.

Buckwheat (Fagopyrum esculentum Moench.) thin cell-layers (TCLs) cultured individually in a liquid medium were used to test the root-inducing activity of pectic polysaccharides with a degree of polymerization (DP) of 20-25, isolated from pea (Pisum sativum L.) stem cell walls. These pectic fragments induced more rapid root formation on the explants in comparison with untreated controls. This pectic fragment treatment also promoted root growth as measured by both fresh and dry weights and about doubled the number of roots formed. This buckwheat TCL system is proposed as a new bioassay for oligosaccharins due to its sensitivity, reproducibility and ease of preparation.