Biological properties and relative fitness of inter-subgroup cucumber mosaic virus RNA 3 recombinants produced in vitro.

In vitro reverse transcription of a mixture of total RNA from plants infected with the I17F or R strains of cucumber mosaic virus (CMV), representative of subgroups IA and II, respectively, results in viral cDNA populations including rare recombinant RNA 3 molecules, some of which also have point mutations. The biological properties of 17 recombinants in the capsid gene or the 3' non-coding region of RNA 3 were evaluated when associated with I17F RNAs 1 and 2. Six viruses displayed deficiencies (non-viability, deficiencies for movement and/or replication, delayed infection, loss of aphid transmissibility).

Stress induces the expression of AtNADK-1, a gene encoding a NAD(H) kinase in Arabidopsis thaliana.

A novel Arabidopsis thaliana gene (AtNADK-1) was identified based on its response to radiation and oxidative stress. Levels of AtNADK-1 mRNA increase eight-fold following exposure to ionising radiation and are enhanced three-fold by treatment with hydrogen peroxide. The gene also appears to be differentially regulated during compatible and incompatible plant-pathogen interactions in response to Pseudomonas syringae pv.

A novel strategy for creating recombinant infectious RNA virus genomes.

Reverse transcriptases with RNase H activity are particularly apt to switch templates and generate recombinant molecules in vitro. This property has been exploited for the first time to create a library of recombinant RNAs 3 between two strains of Cucumber mosaic virus (CMV) or between CMV and Tomato aspermy virus (TAV), which share 75 and 63% sequence identity, respectively. The recombination events were almost entirely of the precise homologous type, and occurred at the same sites as those previously identified in co-infected plants, making it possible to use this strategy to create numerous cDNA fragments with crossovers similar to those occurring in vivo.