Choline-betaine pathway contributes to hyperosmotic stress and subsequent lethal stress resistance in Pseudomonas protegens SN15-2

Pseudomonas protegens SN15-2, a typical non-spore-forming rhizosphere bacterium, has excellent biocontrolcapabilities; thus, it is necessary to explore the stress resistance of SN15-2. The choline–glycine betainepathway is considered as an important mechanism by which bacteria adapt to stressful environments. In thiswork, we demonstrated that the expression of the betA and betB genes, which are involved in the choline–glycine betaine pathway in SN15-2, was highly increased by 12-fold and 26-fold, respectively, by hyperosmotic stress and choline treatment. The accumulation of betaine in SN15-2 (5.54 g/L) was significantly higherthan that in the mutants D betA (3.44 g/L) and D betB (2.68 g/L) under hyperosmotic stress and cholinetreatment. Moreover, choline enhanced the growth of SN15-2 greatly, but it did not enhance the growth of DbetB under hyperosmotic stress. Choline combined with hyperosmotic adaptation significantly increased thelethal stress resistance of SN15-2 while the resistance of D betA and D betB was significantly decreased. Thisresearch illuminated a strategy underlying the adaptation to osmotic stress in P. protegens and provided aneffective method to improve the stress resistance of this species, thus provided a theoretical basis for thepractical application of P. protegens SN15-2.

Cloning, characterization and promoter analysis of common carp hairy/Enhancer-of-split-related gene, her6.

Some members of hairy/Enhancer-of-split-related gene (HES) family have important effects on axial mesoderm segmentation and the establishment and maintenance of the somite fringe. In fishes, the her6 gene, a member of the HES family, is the homologue of hes1 in mammals and chicken. In this study, the her6 gene and its full-length cDNA from the common carp (Cyprinus carpio) were isolated and characterized. The genomic sequence of common carp her6 is approximately 1.7 kb, with four exons and three introns, and the full-length cDNA of 1314 bp encodes a putative polypeptide of 271 amino acids. To analyse the promoter sequence of common carp her6, sequences of various lengths upstream from the transcription initiation site of her6 were fused to enhanced green fluorescent protein gene (eGFP) and introduced into zebrafish embryos by microinjection to generate transgenic embryos. Our results show that the upstream sequence of 500 bp can direct highly efficient and tissue-specific expression of eGFP in zebrafish embryos, whereas a fragment of 200 bp containing the TATA box and a partial suppressor of hairless paired site sequence (SPS) is not sufficient to drive eGFP expression in zebrafish embryos.