Ethylene supports colonization of plant roots by the mutualistic fungus Piriformospora indica

The mutualistic basidiomycete Piriformospora indica colonizes roots of mono- and dicotyledonous plants, and thereby improves plant health and yield. Given the capability of P. indica to colonize a broad range of hosts, it must be anticipated that the fungus has evolved efficient strategies to overcome plant immunity and to establish a proper environment for nutrient acquisition and reproduction. Global gene expression studies in barley identified various ethylene synthesis and signaling components that were differentially regulated in P. indica-colonized roots. Based on these findings we examined the impact of ethylene in the symbiotic association. The data presented here suggest that P. indica induces ethylene synthesis in barley and Arabidopsis roots during colonization. Moreover, impaired ethylene signaling resulted in reduced root colonization, Arabidopsis mutants exhibiting constitutive ethylene signaling, -synthesis or ethylene-related defense were hyper-susceptible to P. indica. Our data suggest that ethylene signaling is required for symbiotic root colonization by P. indica

PARTICLE IDENTIFICATION IN SOLID-STATE DETECTORS BY EXPLOITING PULSE SHAPE INFORMATION

The pulse shapes of current signals were investigated for various silicon detectors of 450 to 2000 mum thickness irradiated with reaction products from S-32 (795 MeV) + Au and C-12 (380 MeV) + Ho. Particle information was found to be present not only in the rise time, but also in the pulse length and in the ratio of charge samples taken at different times. By integrating the whole current signal as well as a defined pulse fraction by means of two QDC channels with different (long and short) integration gates we were able to obtain simultaneously energy and particle information. This simple and cheap technique of signal processing which has already been used for large phoswich arrays has proved to be well suited for the 4pi solid-state multidetector ("Silicon Ball") which is presently under construction at the Hahn-Meitner-Institut. Charge numbers up to Z = 16 are resolved for fast intermediate-mass fragments

Generation of doubled haploid transgenic wheat lines by microspore transformation.

Microspores can be induced to develop homozygous doubled haploid plants in a single generation. In the present experiments androgenic microspores of wheat have been genetically transformed and developed into mature homozygous transgenic plants. Two different transformation techniques were investigated, one employing electroporation and the other co-cultivation with Agrobacterium tumefaciens. Different tissue culture and transfection conditions were tested on nine different wheat cultivars using four different constructs. A total of 19 fertile transformants in five genotypes from four market classes of common wheat were recovered by the two procedures. PCR followed by DNA sequencing of the products, Southern blot analyses and bio/histo-chemical and histological assays of the recombinant enzymes confirmed the presence of the transgenes in the T0 transformants and their stable inheritance in homozygous T1∶2 doubled haploid progenies. Several decisive factors determining the transformation and regeneration efficiency with the two procedures were determined: (i) pretreatment of immature spikes with CuSO4 solution (500 mg/L) at 4°C for 10 days; (ii) electroporation of plasmid DNA in enlarged microspores by a single pulse of ∼375 V; (iii) induction of microspores after transfection at 28°C in NPB-99 medium and regeneration at 26°C in MMS5 medium; (iv) co-cultivation with Agrobacterium AGL-1 cells for transfer of plasmid T-DNA into microspores at day 0 for <24 hours; and (v) elimination of AGL-1 cells after co-cultivation with timentin (200-400 mg/L)

Characterization of MT1 (128/Xyl, cf. Fig. S1e) transformants.

<p>(A) PCR analysis of 13 randomly chosen doubled-haploid T₁ seedlings of primary transformant MT1 B4. Lanes: 1 = 1 kb ladder; 2 =  plasmid DNA; 3 =  wild type wheat DNA; 4–16 = T₁ seeds. (B) Southern blot analysis of homozygous MT1 transformants from T₁ seedlings with the xylanase gene. Lanes: C1, C2, C4 respectively showing 2, 4 and 8 copies of 837 bp probe; M =  DNA ladder; lanes 1–10 = T₁ doubled-haploid seedlings of 6 different T₀ transformants (1 and 2 = MT1-1, 3 and 4 = MT1-2, 5 and 6 = MT1-3, 7 = MT1B5, 8 and 9 = MT1-6, and 10 = MT1-7); lanes 11–13 = T₁ doubled-haploid seedlings of MT1-B4; lanes 14–15 =  wild type DNA. (C) Zymogram assay for identification of transgenic wheat grains synthesizing recombinant 1,4-β-xylanase. Transgenic wheat grains (T₂ of MT1-B4) secrete the enzyme into the medium containing oat-spelt xylan that is stainable with Congo Red. De-polymerization of the xylan by the enzyme results in an unstained yellow ring around the seed. Wild type wheat grains lack the yellow ring (arrows).</p

Electron micrographs of wheat microspores after pretreatment using transmission electron microscopy.

<p>Figures a-c show differences in thickness of intine, number of cytoplasmic organelles and amount of starch accumulated in amyloplasts. (A) represents type I developmental pathway, (B) represents type II developmental pathway, and (C) represents type III developmental pathway. am =  amyloplast, ex =  exine wall, in =  intine layer, mt =  mitochondria, gl =  Golgi apparatus, p =  proplastid, rer =  rough endoplasmic reticulum, st =  starch.</p

Developmental pathways of pre-treated wheat microspores in culture, as determined by time-lapse tracking.

<p>According to the type of development, microspores are grouped into three classes: type I (A–H), type II (I–O) and type III (P–R). Microspores were stained with FM 4–64 (Molecular Probes Cat. # T-3166) to confirm their viability in culture. All pictures were taken at a 25× magnification and 6× optical zoom except for G, O and H, where the former two pictures were taken at the same magnification but at 3× optical zoom and the latter picture was taken at 10× magnification and 1.7× optical zoom.</p