Temporal,cell-specific,and tissue-preferential expression of myrosinase genes during embryo and seedling development in Sinapis alba

The expression of the genes for two types of myrosinase (EC 3.2.3.1), designated MA and MB, during embryo and seedling development was investigated in Sinapis alba L. by in-situ and RNA slot-blot analyses. The expression of MA and MB genes followed similar temporal profiles during embryogenesis, but MB mRNA was present in considerably higher amounts than MA mRNA. In the embryo, both MA and MB genes are activated in cotyledons and axis. The MB genes are preferentially expressed in the cotyledons whereas MA genes are preferentially expressed in the axis. In the developing seedling, MA mRNA was not present in the organs investigated. By contrast, MB mRNA was found in appreciable amounts in hypocotyls, cotyledons and developing leaves. The MB genes seem to be activated preferentially in tissues undergoing rapid cell division and — or cell expansion.Abbreviations DAP days after pollination - MA, MB A type, B type myrosinases in Sinapis alba Anna-Stina Höglund (Uppsala Genetic Center) is gratefully acknowledged for valuable discussion, Anders Gobl (Department of Immunology, Uppsala University) for kindly advice with the labeling of probes and Qingzhu Zhai (Department of Pharmaceutical Biosciences, Uppsala University) for help with seed harvest. This work was supported by grants from the Swedish Research Council for Forestry and Agriculture.     

Soil properties and seedling establishment in soils from monodominant and high-diversity stands of the tropical deciduous forests of México

Abstract. The hypothesis that soils from mature monodominant forests are unfavourable for establishment of tree species other than the dominant was tested for a lowland tropical deciduous forest with stands dominated by Celaenodendron mexicanum Standl. (CS). This species of Euphorbiaceae occurs almost exclusively in monodominant stands in which recruitment of other species appears to be poor. Soil properties were examined and experiments were conducted on germination and establishment of Celaenodendron mexicanum and three other species common in adjacent high-diversity mixed stands (MS): Recchia mexicana Moc. & Sessé, Caesalpinia eriostachys Benth., and Cordia alliodora (Ruiz & Pav.) Oken. Soil moisture regimes are affected by topographic position in the study area, but Celaenodendron mexicanum was found occupying hillsides as well as flatlands, and slope gradients of its stands were typical of the region. The microsites occupied in relation to soil moisture and light availability also appear to be undistinctive. There were no significant differences between stand types in any soil property (pH, O.C., total N, total P, avail. P, K, Ca, Mg, Na, Mn, Fe, Cu, Zn concentrations). A stand of intermediate dominance of Celaenodendron (ICS) did not differ from its adjacent mixed stand (MS) in soil texture or most of the nutrients tested; however, seasonally restricted differences in the contents of Fe and Mn (ICSCaesalpinia eriostachys established in both stand types. The results suggest that the distinction between monodominance and high diversity is not maintained by some simple physiological restriction on the establishment of new seedlings.     

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     

Reduced generation time of apple seedlings to within a year by means of a plant virus vector: a new plant‐breeding technique with no transmission of genetic modification to the next generation

Fruit trees have a long juvenile phase. For example, the juvenile phase of apple (Malus × domestica) generally lasts for 5–12 years and is a serious constraint for genetic analysis and for creating new apple cultivars through cross‐breeding. If modification of the genes involved in the transition from the juvenile phase to the adult phase can enable apple to complete its life cycle within 1 year, as seen in herbaceous plants, a significant enhancement in apple breeding will be realized. Here, we report a novel technology that simultaneously promotes expression of Arabidopsis FLOWERING LOCUS T gene (AtFT) and silencing of apple TERMINAL FLOWER 1 gene (MdTFL1‐1) using an Apple latent spherical virus (ALSV) vector (ALSV‐AtFT/MdTFL1) to accelerate flowering time and life cycle in apple seedlings. When apple cotyledons were inoculated with ALSV‐AtFT/MdTFL1 immediately after germination, more than 90% of infected seedlings started flowering within 1.5–3 months, and almost all early‐flowering seedlings continuously produced flower buds on the lateral and axillary shoots. Cross‐pollination between early‐flowering apple plants produced fruits with seeds, indicating that ALSV‐AtFT/MdTFL1 inoculation successfully reduced the time required for completion of the apple life cycle to 1 year or less. Apple latent spherical virus was not transmitted via seeds to successive progenies in most cases, and thus, this method will serve as a new breeding technique that does not pass genetic modification to the next generation.