S‐locus diversity and cross‐compatibility of wild Prunus avium for timber breeding

Prunus avium is primarily cultivated for its fruit, sweet cherries. However, it is also used to produce high‐quality timber. In a P. avium seed orchard, gametophytic self‐incompatibility is a restriction for free pollen flow and should be considered when establishing basic forest materials. In this study, S‐locus diversity and cross‐incompatibility of wild cherry individuals in clonal banks established for breeding for timber production were investigated. Wild cherry trees (140) with outstanding forest growth habit, collected in northern Spain, grafted and planted in two clonal banks, were genotyped at the S‐locus. The self‐incompatibility S‐locus genes, S‐RNase and SFB, were analysed by PCR. Twenty‐two S‐haplotypes, resulting in 72 different S‐genotypes, were identified. The genotypes were grouped into 33 incompatibility groups and 39 unique genotypes. This initial S‐locus analysis revealed large genetic diversity of wild cherry trees from the Spanish northern deciduous forest, and provides useful information for seed orchard design. Wild P. avium displays significantly more genetic diversity than what is detected in local cultivars, revealing a narrowing of genetic diversity during local domestication.     

Evaluation of carbon sources,gelling agents,growth hormones and additives for efficient callus induction and plant regeneration in Indian wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) genotypes using mature embryos

Various factors affecting in vitro regeneration like different carbon sources, different gelling agents, and growth additives were assessed comprehensively for callus induction and plant regeneration for five Indian wheat cultivars using mature embryos as the explants for the first time. The tissue culture responses of cultivars WH-1105, HD-2967, and PBW-343 have not been reported earlier. Besides, the effect of different concentrations of the cytokinin, zeatin has also been optimized. Using the optimized factors, the efficiency of five different varieties, i.e., HD 2967, C 306, RAJ 3765, WH 1105, and PBW 343 was evaluated for regeneration. Modified MS basal medium containing dicamba reduced precocious germination of the embryo and induced embryogenic callus more efficiently. Removal of embryogenic calli from non-regenerable structures during early callus phase improved plant regeneration. These calli on zeatin (1.0 mgl^-1) and dicamba (0.1 mgl^-1) containing medium showed the highest regeneration frequency (98%) with a maximum of 8-9 shoots per calli. Maltose had the maximum callusing and regeneration percentage than other carbon sources. Various gelling agents did not have any significant difference on the regeneration. Of all the varieties, C-306 and HD-2967 were found to be more regenerative and can be used in transformation experiments.     

大豆品种的再生性能及对EHA 101农杆菌的敏感性

大豆转化可利用农杆菌和子叶节转化系统,bar基因作为选择标记,草丁膦作为选择试剂.用5-6 d发芽的种子的子叶节作外植体,在子叶节处划5-6下,用含pPTN 140的农杆菌EHA 101感染后,共培养3 d,用含抗生素的洗液洗去外植体上的农杆菌,将外植体放入5 mg/L草丁膦的长芽培养基,两周后统计不同大豆品种的再生率,4周后做GUS染色对含pPTN1     

SSR and STS markers for wheat stripe rust resistance gene <Emphasis Type="Italic">Yr26</Emphasis>

Stripe (yellow) rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most devastating wheat diseases worldwide. Triticum aestivum-Haynaldia villosa 6VS/6AL translocation lines carrying the Yr26 gene on chromosome 1B, are resistant to most races of Pst used in virulence tests. In order to better utilize Yr26 for wheat improvement, we attempted to screen SSR and EST-based STS markers closely linked with Yr26. A total of 500 F₂ plants and the F_2:3 progenies derived from a cross between 92R137 and susceptible cultivar Yangmai 5 were inoculated with race CYR32. The analysis confirmed that stripe rust resistance was controlled by a single dominant gene, Yr26. Among 35 pairs of genomic SSR markers and 81 pairs of STS markers derived from EST sequences located on chromosome 1B, Yr26 was flanked by 5 SSR and 7 STS markers. The markers were mapped in deletion bins using CS aneuploid and deletion lines. The closest flanking marker loci, Xwe173 and Xbarc181, mapped in 1BL and the genetic distances from Yr26 were 1.4 cM and 6.7 cM, respectively. Some of these markers were previously reported on 1BS. Eight common wheat cultivars and lines developed from the T. aestivum-H. villosa 6VS/6AL translocation lines by different research groups were tested for presence of the markers. Five lines with Yr26 carried the flanking markers whereas three lines without Yr26 did not. The results indicated that the flanking markers should be useful in marker-assisted selection for incorporating Yr26 into wheat cultivars.     

Levels of host plant resistance to banana weevil, Cosmopolites sordidus (Germar) (Coleoptera: Curculionidae), in African Musa germplasm

Forty-five Musa clones, including endemic and introduced cultivars plus hybrids, were evaluated for resistance against the banana weevil, Cosmopolites sordidus, in a field trial in Uganda. The predominant groups of staple crops, East African highland bananas (Musa spp. AAA) and plantains (Musaspp. AAB), as well as plantain-derived hybrids (AAB × AA), showed the highest levels of susceptibility to this pest. These were followed by dessert bananas (Musa spp. AAA), exotic bananas (Musa spp. ABB) and finally diploids of M. acuminata (AA). Hybrids of banana origin were highly resistant. Some East African highland cultivars, especially brewing types (e.g., Kabula, Bagandeseza, Ediirira), showed intermediate levels of resistance. Among the non-highland bananas, high levels of resistance were observed in Yangambi-Km5 (AAA), Cavendish (AAA), Gros Michel (AAA), Kayinja (ABB, Pisang Awak subgroup), Ndiizi (AB, Ney Poovan subgroup)and Kisubi (Ney Poovan subgroup). The highest resistance was observed in banana hybrids TMB2×7197-2, TMB2×8075-7 and the wild banana Calcutta-4 (AA). These were considered the best sources of resistance for a weevil resistance-breeding programme with the two hybrids commonly used as improved male parents. This revised version was published online in July 2006 with corrections to the Cover Date.     

Novel fluorogenic substrates for assaying retroviral proteases by resonance energy transfer

The 11-kD protease (PR) encoded by the human immunodeficiency virus 1 (HIV-1) is essential for the correct processing of viral polyproteins and the maturation of infectious virus, and is therefore a target for the design of selective acquired immunodeficiency syndrome (AIDS) therapeutics. To facilitate the identification of novel inhibitors of HIV-1 PR, as well as to permit detailed studies on the enzymology and inhibition of this enzyme, a continuous assay for its activity was developed that was based on intramolecular fluorescence resonance energy transfer (RET). The assay used the quenched fluorogenic substrate 4-(4-dimethylaminophenylazo)benzoic acid (DABCYL)--Ser Gln Asn Tyr Pro Ile Val Gln--5-[(2-aminoethyl)amino]naphthalene-1 sulfonic acid (EDANS), whose peptide sequence is derived from a natural processing site for HIV-1 PR. Incubation of recombinant HIV-1 PR with the fluorogenic substrate resulted in specific cleavage at the Tyr-Pro bond and a time-dependent increase in fluorescence intensity that was linearly related to the extent of substrate hydrolysis. An internally quenched fluorogenic substrate was also designed that was selectively cleaved by the related PR from avian myeloblastosis virus (AMV). The fluorescence quantum yields of the HIV-1 PR and AMV PR substrates in the RET assay increased by 40.0- and 34.4-fold, respectively, per mole of substrate cleaved. Because of its simplicity, rapidity, and precision in the determination of reaction rates required for kinetic analysis, this method offers many advantages over the commonly used high-performance liquid chromatography- or electrophoresis-based assays for peptide substrate hydrolysis by retroviral PRs.     

No specific recognition of leader peptide by SecB, a chaperone involved in protein export

Most proteins destined for export from Escherichia coli are made as precursors containing amino-terminal leader sequences that are essential for export and that are removed during the process. The initial step in export of a subset of proteins, which includes maltose-binding protein, is binding of the precursor by the molecular chaperone SecB. This work shows directly that SecB binds with high affinity to unfolded maltose-binding protein but does not specifically recognize and bind the leader. Rather, the leader modulates folding to expose elements in the remainder of the polypeptide that are recognized by SecB.     

Odor stimuli trigger influx of calcium into olfactory neurons of the channel catfish

Olfactory transduction is thought to be mediated by a G protein-coupled increase in intracellular adenosine 3',5'-monophosphate (cAMP) that triggers the opening of cAMP-gated cation channels and results in depolarization of the plasma membrane of olfactory neurons. In olfactory neurons isolated from the channel catfish, Ictalurus punctatus, stimulation with olfactory stimuli (amino acids) elicits an influx of calcium that leads to a rapid increase in intracellular calcium. In addition, in a reconstitution assay a plasma membrane calcium channel has been identified that is gated by inositol-1,4,5-trisphosphate (IP3), which could mediate this calcium influx. Together with previous studies indicating that stimulation with olfactory stimuli leads to stimulation of phosphoinositide turnover in olfactory cilia, these data suggest that an influx of calcium triggered by odor stimulation of phosphoinositide turnover may be an alternate or additional mechanism of olfactory transduction.     

Identification of mutations in the COL4A5 collagen gene in Alport syndrome

X-linked Alport syndrome is a hereditary glomerulonephritis in which progressive loss of kidney function is often accompanied by progressive loss of hearing. Ultrastructural defects in glomerular basement membranes (GBM) of Alport syndrome patients implicate an altered structural protein as the cause of nephritis. The product of COL4A5, the alpha 5(IV) collagen chain, is a specific component of GBM within the kidney, and the gene maps to the same X chromosomal region as does Alport syndrome. Three structural aberrations were found in COL4A5, in intragenic deletion, a Pst I site variant, and an uncharacterized abnormality, which appear to cause nephritis and deafness, with allele-specific severity, in three Alport syndrome kindreds in Utah.     

Autocatalytic oxidation of lead crystallite surfaces

Growth of an ultrathin lead oxide layer causes massive changes in the shape of lead crystallites. The dynamics of this process was investigated with time-lapsed scanning tunneling microscopy. Pure lead crystallites proved extremely resistant to oxidation. Once nucleated by surface impurities, monolayer films of lead oxide grew readily on lead (111) microfacets in an autocatalytic process. The anisotropic growth of orthorhombic lead oxide films (massicot structure) was most rapid along the direction of weakest lead-oxygen bonding, which suggests that the growth edge autocatalyzes oxygen dissociation by providing proximal sites for oxygen dissociation and attachment.