Once again, wrong measurements of plant water status are used in the evaluation of transgenic plants, unnoticed by the reviewers and the editors of a respected journal such as Euphytica. This time it is courtesy of the Department of Vegetative Cellular Biotechnology, The institute of Chemistry and Biology, Portugal. 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 measurement. Very interestingly, in the results (Fig.8-B) they present these values as "relative water content" (RWC). Somehow they heard about RWC as a legitimate measure of plant water status, but they chose to invent their own version here.

It never fails to amaze us how certain molecular biologists are so meticulous in performing molecular protocols to the letter while they assume that plant stress measurements can be invented from the top of their heads.

Euphytica (2005) 146: 165–176

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

Andr´e M. Almeida1,∗, Enrique Villalobos2, Susana S. Ara´ujo1, Barbara Leyman3, Patrick Van Dijck3, Lu´ıs Alfaro-Cardoso4, Pedro S. Fevereiro1,5, Jos´e M. Torn´e2 & Dulce M. Santos6

1Laborat´orio de Biotecnologia de C´elulas Vegetais, Instituto de Tecnologia Qu´ımica e Biol´ogica (ITQB), Oeiras, Portugal; 2Instituto de Biologia Molecular de Barcelona – CSIC, Barcelona, Spain; 3Laboratorium voor moleculaire celbiologie, Katholieke Universiteit Leuven and Vlaams Interuniversitair Instituut voor Biotechnologie (VIB), Leuven-Heverlee, Belgium; 4Instituto de Investigac¸ ˜ao Cientifica e Tropical, Lisboa, Portugal; 5Departamento de Biologia Vegetal, Faculdade de Ciˆencias da Universidade de Lisboa, Lisboa, Portugal; 6Present address: Laborat ´orio de Biologia Funcional de Plantas, Instituto de Biologia Molecular e Celular (IBMC), Porto, Portugal (∗author for correspondence: e-mail: amalmeid@itqb.unl.pt)

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.