Comparison of somatic and sexual Brassica napus - Sinapis alba hybrids and their progeny by cytogenetic studies and molecular characterization.

Reciprocal crosses were performed between Brassica napus (AACC, 2n = 38) cv. Brutor and Sinapis alba (SalSal, 2n = 24) cv. Carine. Using fertilized ovary culture, 2.2 and 1.9% of interspecific hybrids were produced when white mustard was the female and the male parent, respectively. On S. alba cytoplasm, three plants with a BC1-like structure (SalSalAC, 2n = 43) were obtained and ACSal (2n = 31) and AACCSal (2n = 50) hybrids on reciprocal crosses. At the same ploidy level, no differences in meiotic behavior were observed. The amphidiploids (AACCSalSal, 2n = 62), produced after colchicine treatment of ACSal hybrids, were compared with the somatic hybrids previously obtained from the same parental varieties. Only two somatic hybrids differed and one of them lost Idh-2 rapeseed isozymes, whereas all the plants presented an hybrid pattern for all the other molecular markers. The plants with 50 chromosomes (AACCSal) from sexual hybrids were similar whatever their origins. Their comparison with back-cross progeny of somatic hybrids revealed that the latter one differed either by chromosome number, ranging from 42 to 54, or by the percentage of cells with less than 12 univalents and with multivalents. From our results, the efficiency of protoplast fusion compared with sexual crosses as a tool to introduce new traits in a crop is discussed.     

Biochemical, immunological and physicochemical comparisons between OHIO-1 and four SHV-type β-lactamases

The biochemical, immunological and physicochemical properties of the beta-lactamase OHIO-1 were compared to those of four beta-lactamases commonly found in Klebsiella pneumoniae: SHV-1, SHV-3 and the beta-lactamases of strains GN 11-03 and GN 422. The substrate profile of SHV-1, OHIO-1 and of the beta-lactamases GN 11-03 and GN 422 were similar, while that of SHV-3 appeared comparable to that of the extended spectrum SHV-2. Moreover, anti-TEM-1 serum inactivated OHIO-1 as well as SHV-1 and the beta-lactamases of strains GN 11-03 and GN 422. Analysis of the electrophoretic mobilities, isoelectric points and titration curves demonstrated that OHIO-1 and the 4 other beta-lactamases examined were closely related variants. From these findings it appears that OHIO-1 could be classified among the SHV-type beta-lactamases.     

Improvement of DNA preparation and of PCR cycling in RAPD analysis of marine macroalgæ

In order to avoid the effects of bacterial contamination and the excess of RNA and polysaccharides coming from the cell walls, algal DNA for PCR cycling in RAPD analysis was extracted from protoplasts and purified in a CsCl gradient. Results indicate that RAPD can be efficiently applied to marine algæ and useful to distinguish between different strains or between different species.     

Transformation in the cyanobacterium Synechococcus R2: improvement of efficiency; role of the pUH24 plasmid

Systematic studies of the parameters influencing transformation efficiencies in Synechococcus R2 and its spontaneous pUH24 plasmid-minus variant S60, have led to substantial increases in these frequencies (up to 70 times for R2 and 9 times for S60) compared to those obtained by using previously published procedures. Important factors are the physiological state of the host cells (competence occurs at the transition from first to second exponential phases of growth) and the conditions of expression of the transferred characters (they must be exposed to progressively increasing concentrations of the selective agent). Consistently lower (about 30 times) efficiencies were obtained with the S60 strain, the only difference from the wild-type R2 that could be detected. Physiological functions of the pUH24 plasmid are discussed. The interest of the S60 strain as a host in gene cloning work is discussed in the light of published work suggesting inter-vector recombination in R2.