Assessment of genotoxic effects of 2,4-dichlorophenoxyacetic acid on maize by using RAPD analysis

The herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) is principally used in agriculture and may pose toxic risks to some crops. Thus, the goal of the present study was to evaluate the genotoxic properties of 2,4-D by using randomly amplified polymorphic DNA (RAPD) assay in the root of maize (Zea mays L.) seedlings. For this purpose maize seedlings were treated with aqueous solutions of 2,4-D at concentrations ranging from 0.5. ppm to 2. ppm for 7 days. After the growth, root length, total soluble protein levels and RAPD profiles of the seedlings were analyzed to determine genotoxicity. The results showed that increasing concentrations of 2,4-D caused a decrease in the root length and an increase in the total soluble protein levels of the seedlings. The changes occurred in the RAPD profiles of the root tips following 2,4-D treatment included loss of normal bands and appearance of new bands in comparison to that of the control seedlings. Genomic template stability (GTS), carried out for the qualitative assessment of alterations in RAPD profiles, was also significantly affected by increasing concentrations of 2,4-D. © 2012 Elsevier B.V.

Elucidation of glutamine lipid biosynthesis in marine bacteria reveals its importance under phosphorus deplete growth in Rhodobacteraceae

Marine microorganisms employ multiple strategies to cope with transient and persistent nutrient limitation, one of which, for alleviating phosphorus (P) stress, is to substitute membrane glycerophospholipids with non-P containing surrogate lipids. Such a membrane lipid remodelling strategy enables the most abundant marine phytoplankton and heterotrophic bacteria to adapt successfully to nutrient scarcity in marine surface waters. An important group of non-P lipids, the aminolipids which lack a diacylglycerol backbone, are poorly studied in marine microbes. Here, using a combination of genetic, lipidomics and metagenomics approaches, we reveal for the first time the genes (glsB, olsA) required for the formation of the glutamine-containing aminolipid. Construction of a knockout mutant in either glsB or olsA in the model marine bacterium Ruegeria pomeroyi DSS-3 completely abolished glutamine lipid production. Moreover, both mutants showed a considerable growth cost under P-deplete conditions and the olsA mutant, that is unable to produce the glutamine and ornithine aminolipids, ceased to grow under P-deplete conditions. Analysis of sequenced microbial genomes show that glsB is primarily confined to the Rhodobacteraceae family, which includes the ecologically important marine Roseobacter clade that are key players in the marine sulphur and nitrogen cycles. Analysis of the genes involved in glutamine lipid biosynthesis in the Tara ocean metagenome dataset revealed the global occurrence of glsB in marine surface waters and a positive correlation between glsB abundance and N* (a measure of the deviation from the canonical Redfield ratio), suggesting glutamine lipid plays an important role in the adaptation of marine Rhodobacteraceae to P limitation