Recessive and dominant genes interfere with the vascular transport of Potato virus A in diploid potatoes.
(57/1525)
Resistance to Potato virus A (PVA) was examined in a diploid cross involving Solanum tuberosum subsp. andigena as a resistance source. Hypersensitive resistance (HR) to PVA cosegregated with extreme resistance (ER) to Potato virus Y conferred by the dominant gene Ry(adg) on chromosome XI. Hence, HR to PVA was controlled by a novel, dominant resistance gene closely linked to Ry(adg), or Ry(adg) recognized both viruses but conferred a different type of resistance to each virus. The HR prevented systemic infection with PVA following mechanical inoculation but not following graft inoculation. Another, recessive gene, ra, that may be linked or even allelic with Ry(adg) fully blocked vascular transport of PVA in graft-inoculated plants. Hence, a possibility exists that the genes for the three types of resistance to potyviruses may reside at the same, resistance gene-rich chromosome region syntenic in solanaceous species and might be related. The gene ra acted against all of the three PVA strains tested and, therefore, the avirulence determinants could not be mapped. However, also, PVA strain-specific resistance was found in the progeny. It was overcome by mutations introduced into the viral genome-linked protein and the helper component proteinase and/or the coat protein. (+info)
Identifying the determinants in the equatorial domain of Buchnera GroEL implicated in binding Potato leafroll virus.
(58/1525)
Luteoviruses avoid degradation in the hemolymph of their aphid vector by interacting with a GroEL homolog from the aphid's primary endosymbiotic bacterium (Buchnera sp.). Mutational analysis of GroEL from the primary endosymbiont of Myzus persicae (MpB GroEL) revealed that the amino acids mediating binding of Potato leafroll virus (PLRV; Luteoviridae) are located within residues 9 to 19 and 427 to 457 of the N-terminal and C-terminal regions, respectively, of the discontinuous equatorial domain. Virus overlay assays with a series of overlapping synthetic decameric peptides and their derivatives demonstrated that R13, K15, L17, and R18 of the N-terminal region and R441 and R445 of the C-terminal region of the equatorial domain of GroEL are critical for PLRV binding. Replacement of R441 and R445 by alanine in full-length MpB GroEL and in MpB GroEL deletion mutants reduced but did not abolish PLRV binding. Alanine substitution of either R13 or K15 eliminated the PLRV-binding capacity of the other and those of L17 and R18. In the predicted tertiary structure of GroEL, the determinants mediating virus binding are juxtaposed in the equatorial plain. (+info)
Increased killing of Bacillus subtilis on the hair roots of transgenic T4 lysozyme-producing potatoes.
(59/1525)
Transgenic potato plants expressing the phage T4 lysozyme gene which are resistant to the plant-pathogenic enterobacterium Erwinia carotovora subsp. carotovora have been constructed. The agricultural growth of these potatoes might have harmful effects on soil microbiota as a result of T4 lysozyme release into the rhizosphere. To assess the bactericidal effect of roots, we have developed a novel method to associate the cells of Bacillus subtilis with hair roots of plants and to quantify the survival of cells directly on the root surface by appropriate staining and fluorescence microscopy. With this technique, we found that the roots of potato plants (Desiree and transgenic control lines) without T4 lysozyme gene display measurable killing activity on root-adsorbed B. subtilis cells. Killing was largely independent of the plant age and growth of plants in greenhouse or field plots. Roots from potato lines expressing the T4 lysozyme gene always showed significantly (1.5- to 3.5-fold) higher killing. It is concluded that T4 lysozyme is released from the root epidermis cells and is active in the fluid film on the root surface. We discuss why strong negative effects of T4 lysozyme-producing potatoes on soil bacteria in field trials may not be observed. We propose that the novel method presented here to study interactions of bacteria with roots can be applied not only to bacterial killing but also to interactions leading to growth-sustaining effects of plants on bacteria. (+info)
Absolute structure of N-p-coumaroyloctopamine in elicitor-treated potato tuber tissue.
(60/1525)
Treatment of potato tuber tissue with beta-1,3-oligoglucosaccharide causes an accumulation of N-p-coumaroyloctopamine (1). In order to determine the absolute structure of 1 in potato, optically active 1 was synthesized from (R)-octopamine which had been obtained from the racemic mixture by the fractional crystallization. By comparing the chromatographic behavior of synthetic and naturally-occurring samples with a chiral HPLC analysis, the absolute configuration of 1 in potato was determined to be S. This indicates that the absolute configuration of the octopamine moiety of 1 is opposite to that of octopamine formed in animal tissues. (+info)
Ascorbate biosynthesis in mitochondria is linked to the electron transport chain between complexes III and IV.
(61/1525)
Ascorbic acid is synthesized from galactono-gamma-lactone (GL) in plant tissues. An improved extraction procedure involving ammonium sulfate precipitation of membrane proteins from crude leaf homogenates yielded a simple, quick method for determining tissue activities of galactono-gamma-lactone dehydrogenase (GLDH). Total foliar ascorbate and GLDH activity decreased with leaf age. Subcellular fractionation experiments using marker enzymes demonstrated that 80% of the total GLDH activity was located on the inner mitochondrial membrane, and 20% in the microsomal fraction. Specific antibody raised against potato (Solanum tuberosum L.) tuber GLDH recognized a 56-kD polypeptide in extracts from the mitochondrial membranes but failed to detect the equivalent polypeptide in microsomes. We demonstrate that isolated intact mitochondria synthesize ascorbate in the presence of GL. GL stimulated mitochondrial electron transport rates. The respiration inhibitor antimycin A stimulated ascorbate biosynthesis, while cyanide inhibited both respiration and ascorbate production. GL-dependent oxygen uptake was observed in isolated intact mitochondria. This evidence suggests that GLDH delivers electrons to the mitochondrial electron transport chain between complexes III and IV. (+info)
DNA relatedness among strains of Streptomyces pathogenic to potato in France: description of three new species, S. europaeiscabiei sp. nov. and S. stelliscabiei sp. nov. associated with common scab, and S. reticuliscabiei sp. nov. associated with netted scab.
(62/1525)
The genomic relatedness was evaluated by DNA-DNA hybridization for 23 strains (21 were pathogenic and two were saprophytic strains) isolated from lesions of common and netted scab in France and 19 strains from other countries, including type strains of Streptomyces species. Three genomospecies were defined within the conventional species of Streptomyces scabies, and these genomospecies were different from other pathogenic described species (Streptomyces acidiscabies, Streptomyces caviscabies) based on previously published phenotypic data. Two of these genomospecies (1 and 3) correspond to new species, for which the names Streptomyces europaeiscabiei sp. nov. (with type strain CFBP 4497T) and Streptomyces stelliscabiei sp. nov. (with type strain CFBP 4521T) are proposed. Genomospecies 2 corresponds to S. scabies (with type strain CFBP 4517T = ATCC 49173T), and includes only one French strain. The pathogenic strains associated with netted scab lesions constituted a new species that was named Streptomyces reticuliscabiei sp. nov. (with type strain CFBP 4531T). The G+C content of DNA from the three strains CFBP 4497T (S. europaeiscabiei), CFBP 4521T (S. stelliscabiei), CFBP 4531T (S. reticuliscabiei) was 71.3, 71.0 and 69.8 mol%, respectively. Phylogenetic analysis based on 16S rRNA gene sequences showed that the type strain CFBP 4497T was very similar to the type strain of S. scabies, whereas, the type strain of S. stelliscabiei, CFBP 4521T, was very similar to the type strain of Streptomyces bottropensis. On the basis of 16S rRNA gene sequences, the type strain of S. reticuliscabiei, CFBP 4531T, differed extensively from the other strains of Streptomyces tested. (+info)
A possible role for pyrophosphate in the coordination of cytosolic and plastidial carbon metabolism within the potato tuber.
(63/1525)
The early stages of tuber development are characterized by cell division, high metabolic activity, and the predominance of invertase as the sucrose (Suc) cleaving activity. However, during the subsequent phase of starch accumulation the cleavage of Suc occurs primarily by the action of Suc synthase. The mechanism that is responsible for this switch in Suc cleaving activities is currently unknown. One striking difference between the invertase and Suc synthase mediated cleavage of Suc is the direct involvement of inorganic pyrophosphate (PPi) in the latter case. There is presently no convincing explanation of how the PPi required to support this process is generated in potato (Solanum tuberosum) tubers. The major site of PPi production in a maturing potato tubers is likely to be the reaction catalyzed by ADP-glucose pyrophosphorylase, the first committed step of starch biosynthesis in amyloplasts. We present data based on the analysis of the PPi levels in various transgenic plants altered in starch and Suc metabolism that support the hypothesis that PPi produced in the plastid is used to support cytosolic Suc breakdown and that PPi is an important coordinator of cytosolic and plastidial metabolism in potato tubers. (+info)
Potato leafroll virus protein P1 contains a serine proteinase domain.
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The multi-domain potato leafroll virus replicase protein P1 was expressed in insect cells from the polyhedrin promoter of Autographa californica nucleopolyhedrovirus. Using antisera raised against P1, it was shown that P1 was cleaved near the VPg in insect cells in a manner similar to that in plant cells, to produce a approximately 27 kDa C-terminal fragment. Furthermore, it was shown that the proposed serine proteinase-like domain within P1 is responsible for this processing and that this can occur in a trans (intermolecular) reaction. Four conserved residues within the serine proteinase domain that are essential for catalysis have been identified, consistent with the proposal that this domain comprises a serine proteinase. (+info)