Variability in C(3)-plant cell-wall biosynthesis in a high-CO(2) atmosphere by solid-state NMR spectroscopy.

We have used a frequency-selective rotational-echo double-resonance (REDOR) solid-state NMR experiment to measure the concentrations of glycine-glycine pairs in proteins (and protein precursors) of intact leaves of plants exposed to both high- and low-CO(2) atomospheres. The results are interpreted in terms of differences in cell-wall biosynthesis between plant species. We illustrate this variability by comparing the assimilation of label in cheatgrass and soybean leaves labeled using (15)N-fertilizer and (13)CO(2) atmospheres. Cheatgrass and soybean are both C(3) plants but differ in their response to a high-CO(2) environment. Based on REDOR results, we determined that cheatgrass (a plant that seems likely to flourish in future low-water, high-CO(2) environments) routes 2% of the assimilated carbon label that remains in the leaf after 1 h in a 600-ppm (13)CO(2) atmosphere to glycine-rich protein (or its precursors), a structural component of cell walls cross-linked to lignins. In contrast, soybean under the same conditions routes none of its assimilated carbon to glycine-rich protein.

Effect of growth phase on survival of bromegrass suspension cells following cryopreservation and abiotic stresses.

BACKGROUND AND AIMS: Cryopreservation is a practical method of preserving plant cell cultures and their genetic integrity. It has long been believed that cryopreservation of plant cell cultures is best performed with cells at the late lag or early exponential growth phase. At these stages the cells are small and non-vacuolated. This belief was based on studies using conventional slow prefreezing protocols and survival determined with fluorescein diacetate staining or 2,3,5-triphenyltetrazolium chloride assays. This classical issue was revisited here to determine the optimum growth phase for cryopreserving a bromegrass (Bromus inermis) suspension culture using more recently developed protocols and regrowth assays for determination of survival. METHODS: Cells at different growth phases were cryopreserved using three protocols: slow prefreezing, rapid prefreezing and vitrification. Stage-dependent trends in cell osmolarity, water content and tolerance to freezing, heat and salt stresses were also determined. In all cases survival was assayed by regrowth of cells following the treatments. KEY RESULTS: Slow prefreezing and rapid prefreezing protocols resulted in higher cell survival compared with the vitrification method. For all the protocols used, the best regrowth was obtained using cells in the late exponential or early stationary phase, whereas lowest survival was obtained for cells in the late lag or early exponential phase. Cells at the late exponential phase were characterized by high water content and high osmolarity and were most tolerant to freezing, heat and salt stresses, whereas cells at the early exponential phase, characterized by low water content and low osmolarity, were least tolerant. CONCLUSIONS: The results are contrary to the classical concept which utilizes cells in the late lag or early exponential growth phase for cryopreservation. The optimal growth phase for cryopreservation may depend upon the species or cell culture being cryopreserved and requires re-investigation for each cell culture. Stage-dependent survival following cryopreservation was proportionally correlated with the levels of abiotic stress tolerance in bromegrass cells.