Antisense RNA based down-regulation of RNaseE in E.coli

Background  

Messenger RNA decay is an important mechanism for controlling gene expression in all organisms. The rate of the mRNA degradation directly affects the steady state concentration of mRNAs and therefore influences the protein synthesis. RNaseE has a key importance for the general mRNA decay in E.coli. While RNaseE initiates the degradation of most mRNAs in E.coli, it is likely that the enzyme is also responsible for the degradation of recombinant RNAs. As RNaseE is essential for cell viability and knockout mutants cannot be cultured, we investigated the possibility for a down-regulation of the intracellular level of RNaseE by antisense RNAs. During this study, an antisense RNA based approach could be established which revealed a strong reduction of the intracellular level of RNaseE in E.coli.     

Synthesis of <Emphasis Type="SmallCaps">L</Emphasis>-ascorbic acid in the phloem

Background  

Although plants are the main source of vitamin C in the human diet, we still have a limited understanding of how plants synthesise L-ascorbic acid (AsA) and what regulates its concentration in different plant tissues. In particular, the enormous variability in the vitamin C content of storage organs from different plants remains unexplained. Possible sources of AsA in plant storage organs include in situ synthesis and long-distance transport of AsA synthesised in other tissues via the phloem. In this paper we examine a third possibility, that of synthesis within the phloem.     

Biology and epidemics of Candidatus Liberibacter species,psyllid‐transmitted plant‐pathogenic bacteria

Candidatus Liberibacter species are Gram‐negative bacteria that live as phloem‐limited obligate parasites in plants, and are associated with several plant diseases. These bacteria are transmitted by insects called psyllids, or jumping plant lice, which feed on plant phloem sap. Citrus huanglongbing (yellow shoot) or citrus greening disease is associated with three different species of Ca. Liberibacter – Ca. L. asiaticus, Ca. L. africanus and Ca. L. americanus – all originally found on different continents. Ca. L. asiaticus is the most severe pathogen, spread by Asian citrus psyllid Diaphorina citri and causing devastating epidemics in several countries. Ca. L. africanus occurs in Africa where it is spread by the African citrus psyllid Trioza erytreae. Ca. Liberibacter solanacearum is associated with diseases in several solanaceous plants, and transmitted by potato psyllid Bactericera cockerelli. Zebra chip disease is causing large damage in potato crops in North America. In Europe Ca. Liberibacter solanacearum is associated with diseases of the Apiaceae family of plants, carrot and celery, and transmitted by psyllids Trioza apicalis and Bactericera trigonica. When Ca. Liberibacter is suspected as the disease agent, the diagnosis is confirmed by DNA‐based detection methods. Ca. Liberibacter‐associated plant diseases can be controlled by using healthy plant propagation material, eradicating symptomatic plants, and by controlling the psyllid populations spreading the disease.     

Long-distance transport of <Emphasis Type="SmallCaps">L</Emphasis>-ascorbic acid in potato

Background  

Following on from recent advances in plant AsA biosynthesis there is increasing interest in elucidating the factors contributing to the L-ascorbic acid (AsA) content of edible crops. One main objective is to establish whether in sink organs such as fruits and tubers, AsA is synthesised in situ from imported photoassimilates or synthesised in source tissues and translocated via the phloem. In the current work we test the hypothesis that long-distance transport is involved in AsA accumulation within the potato tuber, the most significant source of AsA in the European diet.