Once again, wrong measurements of plant water status are used in the evaluation of transgenic plants for drought resistance. In this case the researchers tested their transgenic plants for drought response after plants were subjected for several days to drying in a pot. Their preferred "assay for drought tolerance" was percent water in fresh leaves after being dried in the oven until constant weight. This is the reciprocal of percent dry matter in leaves, which has nothing to do with plant water status. In the results (Fig.8-B) they present these values erroneously as "relative water content" (RWC), which is not (see RWC ).

Euphytica (2005) 146: 165–176

Transformation of tobacco with an Arabidopsis thaliana gene involved in trehalose biosynthesis increases tolerance to several abiotic stresses.

André M. Almeida, Enrique Villalobos, Susana S. Araújo, Barbara Leyman, Patrick Van Dijck, Luís Alfaro-Cardoso, Pedro S. Fevereiro, José M. Torné and Dulce M. Santos

From the issue entitled "Special Issue: Genetic Variation for Plant Breeding Selected Papers Presented at the 17th EUCARPIA General Congress 2004, Tulln, Austria"

Summary

Trehalose (a non-reducing disaccharide) plays an important role in abiotic stress protection. It has been shown that using trehalose synthesis genes of bacterial origin, drought and salt tolerance could be achieved in several plants. A cassette harboring the AtTPS1 gene under the control of the CaMV35S promoter and the Bialaphos resistance gene was inserted in the binary plasmid vector pGreen0229 and used for Agrobacterium-mediated transformation of tobacco (Nicotiana tabacum). T0 plants obtained were analyzed by PCR for the presence of AtTPS1 gene. Thirty lines were positive and seeds were germinated on media with 6 mg/l PPT to obtain T1 plants that were grown in the greenhouse to obtain T2 seeds that were germinated on selective media. Lines which seeds showed a 100%survival rate were considered homozygous transgenic T1 lines. Three lines were selected and gene expression confirmed by northern and western blots. Transgenic seeds were germinated on media with different concentrations of mannitol (0, 0.25, 0.5 and 0.75 M) and sodium chloride (0, 0.07, 0.14, 0.2, 0.27 and 0.34 M) to score their tolerance to osmotic stress. Assays were conducted to test the tolerance of transgenic plants to drought (measurement of water percentage as a consequence of water withdrawal), desiccation (measurement of water loss as a consequence leaf detaching) and temperature stresses (germination at 15 ◦C and 35 ◦C). Transgenic tobacco plant lines registered higher germination rates under osmotic and temperature stress situations than did wild-type plants. Responses to drought and desiccation stresses were similar for all plant lines. It can hence be suggested that the heterologous expression of TPS1 gene from Arabidopsis can be used successfully to increase abiotic stress tolerance in model plants and probably in other crops.