Di-2-ethylhexyl phthalate (DEHP) exposure disturbs lipid metabolism in juvenile yellow catfish Tachysurus fulvidraco.

This study was conducted to determine the mechanism by which di-2-ethylhexyl phthalate (DEHP) exposure influences lipid metabolism of juvenile yellow catfish Tachysurus fulvidraco. Fish were exposed to three DEHP concentrations (0, 0·1 and 0·5 mg l-1 DEHP) for 8 weeks. Fatty acid synthase (FAS) activity significantly decreased with increasing DEHP concentrations, the highest value was in the Tween control group, whereas the lowest activities of carnitine palmitoyltransferase (CPT) and lipoprotein lipase (LPL) were in this group. The messenger (m)RNA levels of 6-phospho-gluconate dehydrogenase (6PGD), FAS and acetyl-CoA carboxylase a (ACCa) significantly increased with increasing DEHP concentration, the highest values were in the 0·5 mg l-1 DEHP group. The mRNA level of peroxisome proliferator-activated receptor γ (PPARγ) was lower in Tween control than in fish exposed to 0·1 and 0·5 mg l-1 DEHP. The highest mRNA level of ACCb was in the 0·1 mg l-1 DEHP group. These results indicate that DEHP exposure can disturb lipid metabolism at the enzymatic and mRNA levels in Pelteobagrus fulvidraco.

Identification of RNA editing sites in cotton (Gossypium hirsutum) chloroplasts and editing events that affect secondary and three-dimensional protein structures.

RNA editing can alter individual nucleotides in primary transcripts, which can cause the amino acids encoded by edited RNA to deviate from the ones predicted from the DNA template. We investigated RNA editing sites of protein-coding genes from the chloroplast genome of cotton. Fifty-four editing sites were identified in 27 transcripts, which is the highest editing frequency found until now in angiosperms. All these editing sites were C-to-U conversion, biased toward ndh genes and U_A context. Examining published editotypes in various angiosperms, we found that RNA editing mostly converts amino acid from hydrophilic to hydrophobic and restores evolutionary conserved amino acids. Using bioinformatics to analyze the effect of editing events on protein secondary and three-dimensional structures, we found that 21 editing sites can affect protein secondary structures and seven editing sites can alter three-dimensional protein structures. These results imply that 24 editing sites in cotton chloroplast transcripts may play an important role in their protein structures and functions.

Molecular cloning and characterization of a salinity stress-induced gene encoding DEAD-box helicase from the halophyte Apocynum venetum.

The genes encoding DEAD-box helicases play a key role in various abiotic stresses, including temperature, light, oxygen, and salt stress. A salt-responsive gene, designated AvDH1, was isolated from the halophyte dogbane (Apocynum venetum) by using suppression subtractive hybridization and RACE (rapid amplification of cDNA ends) PCR. The deduced amino acid sequence has nine conserved helicase motifs of the DEAD-box protein family. The AvDH1 gene is present as a single copy in the dogbane genome. This gene is expressed in response to NaCl and not polyethlene glycol (PEG) nor abscisic acid, and its expression increases with time. The transcription of AvDH1 is also induced by low temperature (4 degrees C), but its accumulation first increases then decreases with time. The purified recombinant protein contains ATP-dependent DNA helicase activity, ATP-independent RNA helicase activity, and DNA- or RNA-dependent ATPase activity. The ATPase activity of AvDH1 is stimulated more by single-stranded DNA than by double-stranded DNA or RNA. These results suggested that AvDH1 belonging to the DEAD-box helicase family is induced by salinity, functions as a typical helicase to unwind DNA and RNA, and may play an important role in salinity tolerance.