Biochemical and Molecular Analysis of in vitro conserved Microplants of Solanum tuberosum L.

The present investigation deals with the biochemical and molecular analyses of potato microplants in response to osmotic stress. The findings of this study showed that the chlorophyll content of osmotically stressed cells of potato microplants was significantly decreased compared to the microplants cultivated under non-stressed conditions. In contrast, the total soluble sugar, amino acids and proline concentrations were significantly increased in stressed microplants relative to non-stressed plants. The results also suggested a substantial induction of antioxidants such as non-enzymatic scavenging, superoxidase dismutase (SOD) activity, in osmotic stressed microplants compared to untreated controls. However, the expression of MnSOD showed no induction which suggests that another form of SOD might be attributed to this enzymatic activity in potato microplants. Furthermore, the osmotic stress induced free proline concentrations consistent with upregulation of the proline-associated gene P5CS. This study implies that regulation of reactive oxygen species through the modulation of proline might be associated with osmotic adjustment in potato microplants.</jats:p

Evidence that the recessive bymovirus resistance locus rym4 in barley corresponds to the eukaryotic translation initiation factor 4E gene

Recent studies have shown that resistance in several dicotyledonous plants to viruses in the genus Potyvirus is controlled by recessive alleles of the plant translation initiation factor elF4E or elf(iso)4E genes. Here we provide evidence that the barley rym4 gene locus, controlling immunity to viruses in the genus Bymovirus, corresponds to elF4E. A molecular marker based on the sequence of elF4E was developed and used to demonstrate that elF4E and rym4 map to the same genetic interval on chromosome 3HL in barley. Another genetic marker was developed that detects a polymorphism in the coding sequence of elF4E and consistently distinguishes between rym4 and susceptible barley cultivars of diverse parentage. The elF4E gene product from barley genotypes carrying rym4 and allelic rym5 and rym6 genes, originating from separate exotic germplasm, and a novel resistant allele that we identified through a reverse genetics approach all contained unique amino acid substitutions compared with the wild-type protein. Three-dimensional models of the barley elF4E protein revealed that the polymorphic residues identified are all located at or near the mRNA cap-binding pocket, similarly to recent findings from studies on recessive potyvirus resistance in dicotyledonous plants. These new data complement our earlier observations that specific mutations in bymovirus VPg are responsible for overcoming rym4/5-controlled resistance. Because the potyviral VPg is known to interact with elF4E in dicotyledonous plants, it appears that monocotyledonous and dicotyledonous plants have evolved a similar strategy to combat VPg-encoding viruses in the family Potyviridae