SummaryRecent genetic analyses of longevity in animals have revealed that long-lived strains are more tolerant to environmental stresses. To investigate whether extended longevity in Arabidopsis also correlates with an increase in stress tolerance, the response was tested of 11 lateflowering mutants to the superoxide radical-generating herbicide paraquat. A tight correlation between flowering time and paraquat tolerance was found when plants were exposed to low doses of herbicide. Furthermore, the mutant gigantea (gi-3) with the longest delay in flowering time had a high tolerance level to paraquat-induced oxidative stress. All the tested gi alleles had an increased tolerance to paraquat toxicity compared to wild-type, although the actual levels of tolerance differed. In addition, the gi-3 mutant was more tolerant to hydrogen peroxide. These results suggest that the link between longevity and oxidative stress resistance in plants is similar to that found in animals, implying that this phenomenon may be general for all aerobic organisms.

SummaryThe RNA of satellite tobacco necrosis virus (STNV) is a monocistronic messenger that lacks both a 5Ј cap and a 3Ј poly(A) tail. The STNV trailer contains an autonomous translational enhancer domain (TED) that promotes translation in vitro by more than one order of magnitude when combined with the 5Ј-terminal 173 nt of STNV RNA. We now show that the responsible sequence within the 5Ј region maps to the first 38 nt of the STNV RNA. Mutational analysis indicated that the primary sequence of the STNV 5Ј 38 nt and TED is important for translation stimulation in vitro, but did not reveal a role for the complementarity between the two. Translation of chimeric STNV-cat RNAs in tobacco protoplasts showed that TED promotes translation in vivo of RNAs lacking a cap and/or a poly(A) tail. Similar to in vitro, TED-dependent translation in tobacco was stimulated further by the STNV 5Ј 38 nt.

The dTph1 transposable element family of Petunia hybrida line W138 consists of between 100 and 200 members. A strategy that allows simultaneous detection of individual elements is described. Sequences flanking dTph1 elements are amplified by means of a ligation-mediated PCR. The resulting fragments are locus-specific and can be analysed by polyacrylamide gel electrophoresis. One of the applications of Transposon Display is the isolation of dTph1-tagged genes. Fragments that co-segregate with a mutant phenotype can be extracted from the gel and reamplified, providing access to tagged genes, as demonstrated in a reconstruction experiment. Data on the molecular identification of a phenotypic mutant, isolated in a random tagging experiment is also presented. Upon sequencing, the obtained candidate fragment was found to be identical to part of the previously identified Fbp1 gene.

SummaryTransgene expression in maize cells changed from intronindependent to intron-dependent by an exact exchange of the bar coding region for that of cat. By deletion mapping an approximately 100 nucleotide sequence element at the 5Ј end of the cat coding region was identified that, when inserted at the translation start site of the bar gene, impaired expression. Successive inclusion of the salT intron in the 5Ј untranslated region (UTR) restored expression near to wild-type bar expression levels. A chimeric gfp gene, but not nptII gene, behaved similarly. These observations are in agreement with the view that intronmediated enhancement of transgene expression does not enhance, but rather restores expression of an impaired gene.