Germination ofMusa velutina seeds: Comparison ofin vivo andin vitro systems

Summary In the genusMusa, germination is extremely variable and relatively difficult. Even more difficulties are faced when producing hybrids. The seed yield of hybrids in breeding programs is usually low and often, to ensure the viability and survival of seeds, it is necessary to attempt to germinate a large excess of these seeds. In this context,in vitro embryo culture might be an invaluable tool for obtaining desirable hybrid plants in a short time. Seeds ofMusa velutina were sown in seed trays in a peat-based mixture. Thein vivo seed germination reached 78% but only after 9 mo. Because of this delayed and intermittent germination, embryos were excised from seeds and inoculated onto half-strength Murashige and Skoog (1962) medium, with or without supplementation with various concentrations of gibberellic acid. Light and dark conditions were also used to test their effect on embryo germination. After 2 wk, 82% of embryos germinated in the dark on medium containing 0.1 μM gibberellic acid. Addition of gibberellic acid increased the shoot length and root number over the gibberellic acid-free treatment. Similarly, dark conditions gave a significant increase over light conditions for all the parameters except root number where light or dark conditions did not make any difference. Thus, the present study highlights the importance of various components of thein vitro culture ofMusa embryos and the advantage over direct use of greenhouse-sown seeds both in terms of the time taken to germinate and the final percentage.     

Circumscription of Fulbrightiella gen. nov. and Sherwoodiella gen. nov., Two Novel Genera in the Calotrichaceae (Nostocales,Cyanobacteria)

Three novel strains in Calotrichaceae from tropical habitats were isolated and characterized with regard to their morphology, phylogenetic placement, and secondary structures of conserved domains in the 16S-23S internal transcribed spacer (ITS). The strains fell into two clades formerly identified as Calothrix from freshwater and brackish habitats. Based on both morphology and ecology, they differed from the type species of Calothrix, C. confervicola, which is marine, has wide trichomes with short cells, and narrows abruptly to a hyaline hair. The first clade grouped species with heteropolar filaments widened at the base and narrowed gradually toward the apex but not ending in a hair, with basal heterocytes that are formed in series as the apically placed heterocytes senesce; this clade is being named Fulbrightiella gen. nov., with two named species, F. bharadwajae sp. nov. and F. oahuensis sp. nov. The second clade was comprised of a single species with isopolar trichomes that are untapering as hormogonia, but which widen midfilament and taper toward both ends following growth. These trichomes develop pairs of heterocyte mid-filament, causing fragmentation into heteropolar trichomes with basal heterocytes and ends that taper, but not to a hair. This clade consists of a single species at present, Sherwoodiella mauiensis. With this action, four clades in the Calotrichaceae have been named: Macrochaete, Dulcicalothrix, Fulbrightiella, and Sherwoodiella. Calothrix sensu stricto is truly marine, morphologically distinct, and unsequenced; finding and sequencing the generitype for Calothrix remains as the most important and unfinished task in the revision of the Calotrichaceae.     

Immunogenicity of the Shigella flexneri Serotype Y (SFL124) Vaccine Strain Expressing Cloned Glucosyl Transferase Gene of Converting Bacteriophage SfX

The glucosyl transferase gene (gtr) from bacteriophage phage X (SfX) caused partial conversion of serotype Y (group antigen 3, 4) to X (group antigen 7, 8) when introduced into a candidate vaccine strain of Shigella flexneri serotype Y (SFL124). The gtr gene caused conversion of O-antigens but did not eliminate the adsorption of the corresponding phage SfX. The hybrid strain expressing both group antigens 7, 8 and 3, 4 showed 75% protection when immunized guinea pigs were challenged with a wild-type S. flexneri serotype X strain. No protection was observed against serotype Y challenge, although group antigen 3, 4 was detected in the LPS of the hybrid strain. This suggests the importance of O-antigen immunity in the host defense against shigellosis.     

Dynamics of solute/matric stress interactions with climate change abiotic factors on growth,gene expression and ochratoxin A production by Penicillium verrucosum on a wheat-based matrix

Penicillium verrucosum contaminates temperate cereals with ochratoxin A (OTA) during harvesting and storage. We examined the effect of temperature (25 vs 30 ^oC), CO₂ (400 vs 1000 ppm) and matric/solute stress (-2.8 vs -7.0 MPa) on (i) growth, (ii) key OTA biosynthetic genes and (iii) OTA production on a milled wheat substrate. Growth was generally faster under matric than solute stress at 25 ^oC, regardless of CO₂ concentrations. At 30 ^oC, growth of P. verrucosum was significantly reduced under solute stress in both CO₂ treatments, with no growth observed at -2.8 MPa (=0.98 water activity, a_w) and 1000 ppm CO₂. Overall, growth patterns under solute stress was slower in elevated CO₂ than under matric stress when compared with existing conditions. The otapksPV gene expression was increased under elevated CO₂ levels in matric stress treatments. There was fewer effects on the otanrpsPV biosynthetic gene. This pattern was paralleled with the production of OTA under these conditions. This suggest that P. verrucosum is able to actively grow and survive in both soil and on crop debris under three way interacting climate-related abiotic factors. This resilience suggests that they would still be able to pose an OTA contamination risk in temperate cereals post-harvest.     

Perspectives of pluripotent stem cells in livestock

The recent progress in derivation of pluripotent stem cells(PSCs)from farm animals opens new approaches not only for reproduction,genetic engineering,treatment and conservation of these species,but also for screening novel drugs for their efficacy and toxicity,and modelling of human diseases.Initial attempts to derive PSCs from the inner cell mass of blastocyst stages in farm animals were largely unsuccessful as either the cells survived for only a few passages,or lost their cellular potency;indicating that the protocols which allowed the derivation of murine or human embryonic stem(ES)cells were not sufficient to support the maintenance of ES cells from farm animals.This scenario changed by the innovation of induced pluripotency and by the development of the 3 inhibitor culture conditions to support na?ve pluripotency in ES cells from livestock species.However,the long-term culture of livestock PSCs while maintaining the full pluripotency is still challenging,and requires further refinements.Here,we review the current achievements in the derivation of PSCs from farm animals,and discuss the potential application areas.