Pattern analysis of stem cell differentiation during <Emphasis Type="Italic">in vitro Arabidopsis</Emphasis> organogenesis

Plant somatic cells have the capability to switch their cell fates from differentiated to undifferentiated status under proper culture conditions, which is designated as totipotency. As a result, plant cells can easily regenerate new tissues or organs from a wide variety of explants. However, the mechanism by which plant cells have such remarkable regeneration ability is still largely unknown. In this study, we used a set of meristem-specific marker genes to analyze the patterns of stem cell differentiation in the processes of somatic embryogenesis as well as shoot or root organogenesis in vitro. Our studies furnish preliminary and important information on the patterns of the de novo stem cell differentiation during various types of in vitro organogenesis.     

Levels of genetic diversity at different stages of the domestication cycle of interior spruce in British Columbia

Concerns over the reductionist nature of the domestication of forest-tree species focus on the possibility of potential genetic erosion during this process. To address these concerns, genetic diversity assessments in a breeding zone the Province of British Columbia “interior” spruce (Picea glauca×engelmanni) program was conducted using allozyme markers. Genetic-variation comparisons were made between natural and production (seed orchard) populations as well as seed and seedling crops produced from the same breeding zone’s seed orchard. The natural population sample consisted of a total of 360 trees representing three stands within each of three watersheds present in the Shuswap-Adams low-elevation zone of interior British Columbia. Small amounts of genetic differentiation were observed among the nine natural populations (4%) and this was attributable to extensive gene flow Consequently, the sum of these nine populations was considered as a baseline for the genetic variation present in the breeding zone. The comparisons between the seed orchard and the breeding zone produced a similar percentage of polymorphic loci while the expected hetrozygosity (0.207 vs 0.210) and the average number of alleles per locus (2.7 vs 2.4) were slightly lower in the seed orchard. A total of seven natural populations’ rare alleles were not present in the orchard population, while one allele was unique to the orchard. The %P increased to 70.6% in the seedlot, but dropped to the natural populations level (64.7%) in the plantation. The observed increase in %P was a result of pollen contamination in the orchard. It is suspected that the reduction in the plantation was caused by an unintentional selection in the nursery. Simulated roguing in the orchard did not drastically reduce even if up to 50% of the orchard’s clones were rogued. However, roguing was associated with a reduction in the average number of alleles per locus (i.e., sampling effect). Received: 2 January 1996 / Accepted: 24 May 1996     

Haploid plant regeneration from unpollinated ovule cultures of niger (<Emphasis Type="Italic">Guizotia abyssinica</Emphasis> (L. f.) Cass.)

Haploid plants were regenerated in vitro from unpollinated ovules of niger (Guizotia abyssinica (L. f.) (Cass.) on Murashige and Skoog nutrient medium (MS) supplemented with 10 μM naphthaleneacetic acid or 10 μM NAA + 1.5 μM kinetin and 30 g/l sucrose. Gamborg (B5) medium was the best for plant regeneration (in comparison with MS, Nitsch and Nitsch (NN), and Chu (N6) media) from cultured ovules, and 6.66 and 7.33 ovules of JNC-6 and Ootacamund cultivars were involved in direct plant regeneration on this medium. Matured ovules (ovules collected one day before anthesis or on the day of anthesis) only responded to cultural regimes and involved in direct plantlet development. Cytological preparation of root tips and chloroplast counts in the guard cells of leaf stomata of regenerated plants confirmed their haploid nature. This text was submitted by the authors in English.     

Effects of Juvenoids and Retinoic Acid on Development of Larvae and Nymphs in the Tick Ixodes ricinus L. (Acari,Ixodidae) and Regeneration of Haller's Organ during Metamorphosis

Larvae and nymphs of the tick Ixodes ricinus L. display similar reactions to analogs of the insect juvenile hormones (methoprene and pyriproxyfen), which induce at both stages juvenalization of the Haller's sense organ regenerates. Similar effects were also described for retinoic acid. Unlike juvenoids, retinoic acid can affect not only regeneration, but also normal development of the Haller's organ and cause changes corresponding to so-called regenerative induction. Amputation of the leg and treatment with retinoic acid do not affect the duration of larval or nymphal development, while juvenoids somewhat accelerate their development.     

Optimization of biotin and thiamine requirements for somatic embryogenesis of date palm (Phoenix dactylifera L.)

Summary This study was conducted to examine the effect of biotin and thiamine concentrations on callus growth and somatic embryogenesis of date palm (Phoenix dactylifera L.). Embryogenic callus derived from offshoot tip explants was cultured on hormone-free MS medium containing biotin at 0, 0.1, 1, or 2 mg l⁻¹ combined with thiamine at 0.1, 0.5, 2, or 5 mg l⁻¹. Embryogenic callus weight, number of resultant embryos, and embryo length were significantly influenced by thiamine and biotin concentration. The optimum callus growth treatment consisted of 0.5 mg l⁻¹ thiamine and 2 mg l⁻¹ biotin. This treatment also gave the highest number of embryos. Embryo elongation was greatest at 0.5 or 2 mg l⁻¹ thiamine combined with 1 mg l⁻¹ biotin. Embryos from all treatments germinated and regenerants exhibited normal growth in soil. This study provides an insight into the importance of optimizing various culture medium components to overcome in vitro recalcitrace of date palm.     

Characterization of β-amylase and its deficiency in various rice cultivars

 β-Amylase deficiency in various cultivars of rice was examined at the molecular level. Using an antibody against β-amylase purified from germinating seeds of rice, we were able to demonstrate the expression and organization of the β-amylase gene in normal and deficient cultivars. Although β-amylase is a starch-hydrolyzing enzyme, as is α-amylase, the β-amylase protein/gene is expressed differently from the α-amylase protein/gene; i.e. (1) β-amylase is synthesized only in aleurone cells, (2) the enzyme production in the embryo-less half-seeds is not under hormonal control. We identified some cultivars of rice that are deficient for β-amylase activity. We present new evidence that synthesis is blocked at the level of mRNA synthesis in the deficient cultivars. The usefulness of β-amylase as a crop trait is also discussed. Received: 8 May 1998 / Accepted: 5 June 1998     

Protoplast formation and regeneration in <Emphasis Type="Italic">Lactobacillus delbrueckii</Emphasis>

Method for production and regeneration of Lactobacillus delbrueckii protoplasts are described. The protoplasts were obtained by treatment with a mixture of lysozyme and mutanolysin in protoplast buffer at pH 6.5 with different osmotic stabilizers. The protoplasts were regenerated on deMan, Rogosa and Sharpe (MRS) with various osmotic stabilizers. Maximum protoplast formation was obtained in protoplast buffer with sucrose as an osmotic stabilizer using a combination of lysozyme (1 mg/ml) and mutanolysin (10 μg/ml). Maximum protoplast regeneration was obtained on MRS medium with sucrose (0.5 M) as an osmotic stabilizer. The regeneration medium was also applicable to other species of lactobacilli as well. This is, to our knowledge, the first report on protoplast formation and efficient regeneration in case of L. delbrueckii.