Control of carotenoid gene expression in Bixa orellana L. leaves treated with norflurazon

Bixa orellana (annatto or lipstick tree) is a perennial tropical plant that stores and produces considerable quantities of the apocarotenoid bixin, a culturally and economically important pigment used worldwide. However, the mechanisms underlying the gene regulation and pigment accumulation of bixin and carotenoids in annatto remain unknown. Bixin is present in the different tissues of the plant, although this pigment is primarily accumulated in the seed coat. Thus, the leaves are useful organs for understanding carotenoid and bixin production, thereby facilitating the study of this pigment, which would otherwise be difficult in ligneous adult plants. To study the regulation of bixin synthesis and to determine which genes are important regulatory molecules at the transcription level, the herbicide norflurazon (NF) was used to block carotenoid synthesis and bixin concentrations in B. orellana leaves. The genes activated in the early stages of the carotenoid pathway are involved in lycopene production (dxs, psy and pds), and those induced in the later stages of the carotenoid pathway, such as β and ε-lycopene cyclases and boccd1, were differentially expressed compared with the control. The expression of some genes was more susceptible to certain concentrations of NF, potentially reflecting the roles of these genes in carotenoid synthesis in B. orellana. These results suggest that apocarotenoids, such as bixin, are synthesized using alternative precursors through the actions of genes that have not yet been identified

Antimicrobial peptides produced by bacteria: The bacteriocins

Bacteriocins are the subset of antimicrobial peptides (AMPs) produced by bacteria. They are small amphipathic peptides that interact with bacterial membranes leading to cell death. Most of the best known are produced by lactic acid bacteria used as food fermentation starters, because of their potential use as food preservatives. Bacteriocins are divided into two groups: lantibiotics that present posttranslational condensation rings and unmodified peptides. The first are subdivided into elongated versus globular lantibiotics, while four subgroups are recognized among unmodified bacteriocins. The genetic organization is in clusters that may reside into plasmids or transposons, formed by the structural gene, the export and immunity determinants, the quorum sensing governing production and any modification genes. Bacteriocins are active at extremely low concentrations (nM range) due to a dual mode of action: (a) binding to the membrane phospholipids and (b) specific recognition of surface components, both of which collaborate in pore formation. Development of resistance to bacteriocins is very infrequent due to the presence of two targets and is usually due to unspecific modifications of the cell envelope. Bacteriocins are used as food preservatives, either after total or partial purification or as extracts of producing bacteria. In situ production is also used, with the advantage of producing early lysis of the starter bacteria and ripening acceleration of the fermented product. They may also form part of hurdle technologies and be incorporated into packaging systems to allow extended liberation. Medical and veterinary applications are in their infancy but good results have been obtained against infection by Gram-positive bacteria and Helicobacter pylori.Peer reviewe