Increasing soil salinization of arable land has a major impact on the global ecosystem. One approach to increase the usable global forest area is to develop transgenic trees with higher tolerance to conditions of salt stress. An allene oxide cyclase homolog, mangrin, contains a core protein domain that enhances the salt tolerance of its host. We utilized this feature to develop improved salt-tolerant eucalyptus trees, by using transgenic Eucalyptus camaldulensis carrying the mangrin gene as a model. Since the Japanese government requires an environmental biosafety assessment for the surrounding biosphere, we performed experiments on trees grown in a special netted-house. This study examined the transgenic E. camaldulensis carrying the mangrin gene to assess the feasibility of using these transformants, and assessed their salt tolerance and environmental biosafety. We found that seven of 36 transgenic genotypes had significantly higher salt tolerance than non-transformants, and more importantly, that these plants had no significant impact on environmental biosafety. These results suggest that introduction of the mangrin gene may be one approach to safely enhance salt tolerance in genetically modified Eucalyptus species, and that the transformants have no apparent risks in terms of environmental biosafety. Thus, this study provides valuable information regarding the use of transgenic trees in situ.

Untargeted metabolome analyses play a critical role in understanding possible metabolic fluctuations of crops under varying environmental conditions. This study reports metabolic profiles of transgenic potato tubers expressing the Arabidopsis DREB1A transcription factor gene, which induces expression of genes involved in environmental stress tolerance. A combination of targeted and untargeted metabolomics demonstrated considerable metabolome differences between the transgenic lines and nontransgenic parent cultivars. In the transgenic lines, stimulation of stress responses was suggested by elevated levels of the glutathione metabolite, γ-aminobutyric acid (GABA), and by the accumulation of β-cyanoalanine, a byproduct of ethylene biosynthesis. These results suggest that the Arabidopsis DREB1A expression might directly or indirectly enhance endogenous potato stress tolerance systems. The results indicate that transgenesis events could alter the metabolic compositions in food crops, and therefore metabolomics analysis could be a most valuable tool to monitor such changes.

Note to J Wood Science Allelopathy assessments for the environmental biosafety of the salt-tolerant transgenic Eucalyptus camaldulensis, genotypes codA 12-5B, codA 12-5C and codA 20C

Plantlets of Aeluropus lagopoides (Linn.) Trin. Ex Thw. were grown at different NaCl concentrations (26, 167, 373 and 747 mM) for 3, 7 and 15 days; their growth, osmotic adjustment, gas exchange, ion compartmentalisation and expression of various genes related to Na + flux was studied. Plantlets showed optimal growth in non-saline (control; 26 mM NaCl) solutions, whereas CO 2 /H 2 O gas exchange, leaf water concentration and water use efficiency decreased under all salinity treatments, accompanied by increased leaf senescence, root ash, sodium content and leaf osmolality. A decrease in malondialdehyde (MDA) content with time was correlated with Na + accumulation in the leaf apoplast and a concomitant increase in Na + secretion rate. A. lagopoides accumulated a higher concentration of Na + in root than in leaf vacuoles, corresponding with higher expression of V-NHX and lower expression of PM-NHX in root than leaf tissue. It appears that V-ATPase plays a vital role during Na + transport by producing an electromotive force, driving ion transport. Leaf calcium increased with increasing salinity, with more rapid accumulation at high salinity than at low salinity, indicating a possible involvement of Ca 2+ in maintaining K + : Na + ratio. Our results suggest that A. lagopoides successfully compartmentalised Na + at salinities up to 373 mM NaCl by upregulating the gene expression of membrane linked transport proteins (V-NHX and PM-NHX). At higher salinity (747 mM NaCl), a reduction in the expression of V-NHX and PM-NHX in leaves without any change in the rate of salt secretion, is a possible cause of the toxicity of NaCl.

Transgenic crops able to tolerate environmental stress are being developed throughout the world. However, little data is available on the impact of environmental stress-tolerant transgenic crops on soil microorganisms and biochemistry. Recently developed transgenic potato plants carrying an environmental stress-related gene, DREB1A, with a stress-inducible promoter, are being evaluated for growth performance in greenhouses. In this study, we investigated microbial diversity and soil function to assess potential environmental risks of these transgenic potato lines. Genotypic diversity of the 16S-23S rRNA intergenic spacer region and activity levels of four enzymes were used as indicators of microbial genetic diversity and soil function, respectively. Salinity had a major effect on both bacterial (88-93%) and fungal (54-55%) diversity, while the transgene had a relatively small effect on genotypic structure (0-5%) based on the analysis of variance. However, a few genotypes appeared only in soils planted with the transgenic lines. Some enzyme activities were found to differ significantly between the transgenic and non-transgenic lines, although the results were not repeatable in the second trial. These results suggest that abiotic growth environments had a stronger impact on soil microorganisms and biochemistry than did plant genotypes.