Sex influence on recombination frequency in Secale cereale L.

The variation in recombination frequency (rf) is important to plant breeders since their major objective is to obtain favorable recombinants of linked genes. One source of variation in rf is sex. Sex differences for recombination frequencies were studied in four of the seven chromosomes of Secale cereale L. cv Ailés using isozyme and storage protein loci and were determined on the basis of reciprocal crosses between heterozygous plants of cv. Ailés and homozygous plants of the inbred line Riodeva. The differences were found to be strongly segmentspecific. In some cases the level of crossing-over in male and female meiosis was about the same (between Pgm1 and Ndh1 loci on chromosome arm 4RS). However, for most of the chromosome segments in 1R, 3RL and 6RL the male rf was significantly higher than the female rf. Different hypotheses about the mechanisms of plant sex differences for recombination are discussed.     

Purification and characterization of tomatinase from Fusarium oxysporum f. sp. lycopersici.

The antifungal compound alpha-tomatine, present in tomato plants, has been reported to provide a preformed chemical barrier against phytopathogenic fungi. Fusarium oxysporum f. sp. lycopersici, a tomato pathogen, produces an extracellular enzyme inducible by alpha-tomatine. This enzyme, known as tomatinase, catalyzes the hydrolysis of alpha-tomatine into its nonfungitoxic forms, tomatidine and beta-lycotetraose. The maximal tomatinase activity in the fungal culture medium was observed after 48 h of incubation of germinated conidia at an alpha-tomatine concentration of 20 micrograms/ml. The enzymatic activity in the supernatant was concentrated against polyethylene glycol 35,000, and the enzyme was then purified to electrophoretic homogeneity by a procedure that includes preparative isoelectric focusing and preparative gel electrophoresis as main steps. The purification procedure had a yield of 18%, and the protein was purified about 40-fold. Tomatinase was found to be a monomer of 50 kDa by both native gel electrophoresis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The analytical isoelectric focusing of the native tomatinase showed at least five isoforms with pIs ranging from 4.8 to 5.8. Treatment with N-glycosidase F gave a single protein band of 45 kDa, indicating that the 50-kDa protein was N glycosylated. Tomatinase activity was optimum at 45 to 50 degrees C and at pH 5.5 to 7. The enzyme was stable at acidic pH and temperatures below 50 degrees C. The enzyme had no apparent requirement for cofactors, although Co2+ and Mn2+ produced a slight stimulating effect on tomatinase activity. Kinetic experiments at 30 degrees C gave a K(m) of 1.1 mM for alpha-tomatine and a Vmax of 118 mumol/min/mg. An activation energy of 88 kJ/mol was calculated.     

Sequence similarity of putative transposases links the maize Mutator autonomous element and a group of bacterial insertion sequences.

The Mutator transposable element system of maize is the most active transposable element system characterized in higher plants. While Mutator has been used to generate and tag thousands of new maize mutants, the mechanism and regulation of its transposition are poorly understood. The Mutator autonomous element, MuDR, encodes two proteins: MURA and MURB. We have detected an amino acid sequence motif shared by MURA and the putative transposases of a group of bacterial insertion sequences. Based on this similarity we believe that MURA is the transposase of the Mutator system. In addition we have detected two rice cDNAs in genbank with extensive similarity to MURA. This sequence similarity suggests that a Mutator-like element is present in rice. We believe that Mutator, a group of bacterial insertion sequences, and an uncharacterized rice transposon represent members of a family of transposable elements.     

Characterization of Monoclonal Antibodies Specific for Erwinia carotovora subsp. atroseptica and Comparison of Serological Methods for Its Sensitive Detection on Potato Tubers

Seven monoclonal antibodies (MAbs) to Erwinia carotovora subsp. atroseptica have been produced. One, called 4G4, reacted with high specificity for serogroup I of E. carotovora subsp. atroseptica, the most common serogroup on potato tubers in different serological assays. Eighty-six strains belonging to different E. carotovora subsp. atroseptica serogroups were assayed. Some strains of serogroup XXII also reacted positively. No cross-reactions were observed against other species of plant pathogenic bacteria or 162 saprophytic bacteria from potato tubers. Only one strain of E. chrysanthemi from potato cross-reacted. A comparison of several serological techniques to detect E. carotovora subsp. atroseptica on potato tubers was performed with MAb 4G4 or polyclonal antibodies. The organism was extracted directly from potato peels of artificially inoculated tubers by soaking or selective enrichment under anaerobiosis in a medium with polypectate. MAb 4G4 was able to detect specifically 240 E. carotovora subsp. atroseptica cells per ml by indirect immunofluorescence and immunofluorescence colony staining and after soaking by ELISA-DAS (double-antibody sandwich enzyme-linked immunosorbent assay) after enrichment. The same amount of cells was detected by using immunolectrotransfer with polyclonal antibodies, and E. carotovora subsp. atroseptica and subsp. carotovora were distinguished by the latter technique. ELISA-DAS using MAb 4G4 with an enrichment step also efficiently detected E. carotovora subsp. atroseptica in naturally infected tubers and plants.     

QTL analysis of trichome-mediated insect resistance in potato

Genetic mapping of several components of a complex type of insect resistance has been undertaken as a means toward more efficient use of the valuable characteristics of a wild relative of potato. RFLP maps constructed on interspecific diploid progenies of Solanum tuberosum × S. berthaultii were used in conjunction with morphological, biochemical and biological phenotyping to identify quantitative trait loci (QTLs) contributing to trichome-mediated insect resistance. By superimposing QTL data for a wide range of phenotypes including biochemical assays, correlative and direct screens for insect resistance, and adaptation to the target environment on the genetic maps, we have addressed the organization, action and interaction of genes controlling the resistance mechanism. The outcome contributes to an understanding of the association between component traits and between desirable and undesirable features of the donor species generated in an applied breeding program. Research is proceeding toward the development of selectable markers for the introgression and transfer of this resistance among potato gene pools.     

Retrograde flow of spermatozoa into the urinary bladder of boars during collection of semen by electroejaculation

Boars that had a catheter implanted in the urinary bladder (n = 11) were used to determine the magnitude of retrograde flow of spermatozoa into the urinary bladder during electroejaculation. The overall mean (+/- SD) number of spermatozoa in the electroejaculate of boars was 22 +/- 20 x 10(9), with a mean range for individual boars of 3 +/- 3 to 48 +/- 13 x 10(9). The overall mean adjusted total number of spermatozoa in the post-electroejaculation urine was 1.038 +/- 2.656 x 10(9), and the mean percentage of retrograde flow of spermatozoa into the urinary bladder among boars ranged from 0% to 32.69%, with an overall mean percentage of retrograde flow of 7.51 +/- 17.82%. These findings indicate that in boars electroejaculation is associated with retrograde flow of spermatozoa into the bladder.     

Chromium-induced inhibition of ethylene evolution in bean (Phaseolus vulgaris) leaves

The influence of chromium concentration on ethylene production in bean plants ( Phaseolus vulgaris L. cv. Contender) was investigated. A Cr ion-induced inhibition of ethylene synthesis from endogenous 1-aminocyclopropane-1-carboxylic acid (ACC) was observed within both leaf discs floated on 2 m M CrO²⁻₄ or Cr³⁺ and leaf discs from plants cultured in nutrient solutions containing 10, 20 or 40 μ M CrO²⁻₄. However, Cr ions supplied either to plants with the nutrient solution or to discs with the incubation medium rather increased the conversion of exogenous ACC to ethylene. Primary leaves of plants exposed to CrO²⁻₄-containing nutrient solutions showed a statistically insignificant decrease of ACC-synthase activity. In the trifoliolate leaves of plants exposed to 10 μ M CrO²⁻₄, in which a significant decrease of ethylene production from endogenous ACC was observed, a substantial increase of ACC synthase was found. These results indicate that Cr ion-induced inhibition of ethylene production is not due to a breakdown of membrane integrity, which is necessary for ethylene forming enzyme activity, but caused by metabolic alterations leading to decreased ACC availability. Chromium ions may act by inhibiting ACC synthase activity or by diverting a metabolic step prior to the ACC synthase catalyzed reaction.     

Fine regulation of cI857-controlled gene expression in continuous culture of recombinant Escherichia coli by temperature.

The expression at different temperatures of the lacZ gene, which is controlled by the lambda pL and pR tandem promoters and the cI857 temperature-sensitive repressor, was studied in Escherichia coli continuous cultures. At temperatures between 30 and 42 degrees C, beta-galactosidase activity behaved according to an exponential equation. By inducing a culture at a temperature within this range, predefined, nearly constant submaximal levels of gene expression and recombinant product yield can be obtained.