Genome size and sensitivity to DNA damage by X-rays-plant comets tell the story.

Among several factors affecting radiation sensitivity, genome size has received limited attention during the last 50 years since research at Brookhaven National Laboratory (USA) and other locations demonstrated substantial differences in radiation sensitivities, e.g. between tree species with large (e.

DNA repair after X-irradiation: lessons from plants.

The effects of low-dose radiation causing DNA damage continue to be subjects of interest. Problems with existing approaches to low-dose DNA damage are that single-strand breaks (the predominant radiation-induced lesion) are very rapidly repaired and that results using current methods for measuring DNA damage can be difficult to interpret. As a novel approach, we conducted studies using plants (rye grass and the model plant Arabidopsis) exposed to X-rays and used the alkaline comet assay to measure DNA damage and repair after exposures.

Trace element mobility and transfer to vegetation within the Ethiopian Rift Valley lake areas.

To evaluate critical trace element loads in native vegetation and calculate soil-to-plant transfer factors (TFs), 11 trace elements (Cr, Co, Ni, Cu, Zn, As, Se, Mo, Cd, Pb and Mn) have been determined in leaves of 9 taxonomically verified naturally growing terrestrial plant species as well as in soil samples collected around 3 Ethiopian Rift Valley lakes (Koka, Ziway and Awassa). The Cr concentration in leaves of all the plant species was higher than the "normal" range, with the highest level (8.4 mg per kg dw) being observed in Acacia tortilis from the Lake Koka area.

Glycine betaine enhances extracellular processes blocking ROS signaling during stress.

It has now been demonstrated that treatment of plants with glycine betaine (GB) improves tolerance to chilling stress by regulating gene expression. This finding provides the opportunity to identify new stress determinants using gene expression profiling with microarrays followed by functional confirmation of the involvement of candidate genes via mutant studies. The first gene identified by this approach was the gene for RabA4c GTPase (At5g47960), which is expressed in roots and is involved in vesicle trafficking from the Golgi Apparatus to the plasma membrane.

The FRO2 ferric reductase is required for glycine betaine's effect on chilling tolerance in Arabidopsis roots.

FRO2 (At1g01580) codes for an NADPH-dependent ferric reductase in plasma membranes of root epidermal cells with a demonstrated role in iron uptake by plants. Ferric reductase activity has been shown to be the rate-limiting step for iron uptake in strategy I plants like Arabidopsis and in rice, but it has been unclear whether FRO genes have other physiological functions. We hypothesized that FRO2 was involved in chilling stress tolerance because its expression was upregulated by treatment of plants with glycine betaine (GB), a chemical that prevents reactive oxygen species (ROS) signaling in chilling stress.

ROS Signaling Pathways in Chilling Stress.

It was known that application of glycine betaine (GB) to plants could improve tolerance to stress caused by chilling, frost, salt, drought and high light intensities, and that this effect was accompanied by gene expression changes, but whether the gene expression changes were implicated in GB's effect and which genes were involved has been unclear. In the fourth issue of Physiologia Plantarum, we identified genes upregulated by GB that are involved in reactive oxygen species (ROS) metabolism and membrane trafficking processes. Direct evidence was provided for a role for a membrane trafficking protein (RabA4c) in GB's effect on ROS accumulation during chilling.