ABSTRACT
Abstract Drought stress is the main limiting factor of soybean yield. Currently, genetic engineering has been one important tool in the development of drought-tolerant cultivars. A widely used strategy is the fusion of genes that confer tolerance under the control of the CaMV35S constitutive promoter; however, stress-responsive promoters would constitute the best alternative to the generation of drought-tolerant crops. We characterized the promoter of α-galactosidase soybean (GlymaGAL) gene that was previously identified as highly up-regulated by drought stress. The β-glucuronidase (GUS) activity of Arabidopsis transgenic plants bearing 1000- and 2000-bp fragments of the GlymaGAL promoter fused to the uidA gene was evaluated under air-dried, polyethylene glycol (PEG) and salt stress treatments. After 24 h of air-dried and PEG treatments, the pGAL-2kb led to an increase in GUS expression in leaf and root samples when compared to the control samples. These results were corroborated by qPCR expression analysis of the uidA gene. The pGAL-1kb showed no difference in GUS activity between control and treated samples. The pGAL-2kb promoter was evaluated in transgenic soybean roots, leading to an increase in EGFP expression under air-dried treatment. Our data indicates that pGAL-2kb could be a useful tool in developing drought-tolerant cultivars by driving gene expression.
ABSTRACT
The neuraminidase gene, nanH, is present in the O1, non-toxigenic Vibrio cholerae Amazonia strain. Its location has been assigned to a 150 kb NotI DNA fragment, with the use of pulsed-field gel electrophoresis and DNA hybridization. This NotI fragment is positioned inside 630 kb SfiI and 1900 kb I-CeuI fragments of chromosome 1. Association of the pathogenicity island VPI-2, carrying nanH and other genes, with toxigenic strains has been described by other authors. The presence of nanH in a non-toxigenic strain is an exception to this rule. The Amazonia strain nanH was sequenced (Genbank accession No. AY825932) and compared to available V. cholerae sequences. The sequence is different from those of pandemic strains, with 72 nucleotide substitutions. This is the first description of an O1 strain with a different nanH allele. The most variable domain of the Amazonia NanH is the second lectin wing, comprising 13 out of 17 amino acid substitutions. Based on the presence of nanH in the same region of the genome, and similarity of the adjacent sequences to VPI-2 sequences, it is proposed that the pathogenicity island VPI-2 is present in this strain.