Molecular markers for leaf rust resistance genes in wheat

Over 100 genes of resistance to rust fungi: Puccinia recondita f. sp. tritici, (47 Lr - leaf rust genes), P. striiformis (18 Yr - yellow rust genes) and P. graminis f. sp. tritici (41 Sr - stripe rust genes) have been identified in wheat (Triticum aestivum L.) and its wild relatives according to recent papers. Sixteen Lr resistance genes have been mapped using restriction fragments length polymorphism (RFLP) markers on wheat chromosomes. More than ten Lr genes can be identified in breeding materials by sequence tagged site (STS) specific markers. Gene Lrk 10, closely linked to gene Lr 10, has been cloned and its function recognized. Available markers are presented in this review. The STS, cleaved amplified polymorphic sequence (CAPS) and sequence characterized amplified regions (SCAR) markers found in the literature should be verified using Triticum spp. with different genetic background. Simple sequence repeats (SSR) markers for Lr resistance genes are now also available.     

Resistance to protoporphyrinogen oxidase-inhibiting compound S23142 from overproduction of mitochondrial protoporphyrinogen oxidase by gene amplification in photomixotrophic tobacco cells

Tobacco YZI-IS cells exhibit a 150-fold greater resistance to the protoporphyrinogen oxidase (Protox)-inhibiting compound, S23142, from wild-type tobacco cells. To investigate the mechanism for this S23142 resistance, the protein level, enzymatic activity, and sensitivity to S23142 in two Protox isoenzymes (plastidal and mitochondrial forms) were examined. The level of mitochondrial Protox protein was greater, and its activity 5-times higher, in YZI-IS cells than in wild-type cells. Furthermore, the apparent IC50 value of S23142 was about 20 nM, which is 20-fold higher than that observed in wild-type cells. In contrast, no differences were found in the plastidal Protox protein level, activity or its inhibition by S23142 between YZI-1S and wild-type cells. A southern blot analysis revealed that the mitochondrial Protox gene had been significantly amplified in the YZI-1S cells. These results suggest that the S23142 resistance of YZI-1S cells was due to the overproduction of mitochondrial Protox by gene amplification.     

Assessment of RAPD markers for barley doubled haploid lines resistant and susceptible to Fusarium culmorum at seedling and adult plant growth stages

Thirty doubled haploid (DH) lines of barley derived from F(1) of a cross between the six-rowed cultivar Pomo and two-rowed cultivar Maresi were examined for susceptibility to Fusarium seedling blight (SB) and head blight (FHB), measured by mycotoxin (nivalenol) content of kernels. RAPD (random amplified polymorphic DNA) polymorphism was analysed by using 53 decamer primers. Amplification products (APs) were 200 bp up to 2000 bp in size on average 5.7 per primer and the total number of APs was 284, 51.06% of which were polymorphic. Only 32 APs differentiated the examined DH lines - 19 APs for nivalenol content of kernels and 13 for seedling resistance. DH lines segregated with continuous distribution of resistance to FHB and SB. At the seedling stage all DH lines exhibited lower susceptibility than parental cultivars, but in the adult stage only two lines (MP 2 and MP 7) appeared to be more resistant to FHB, i.e. accumulated in kernels a lower amount of mycotoxin than cultivars Maresi and Pomo.     

Effects of thioredoxin on the preimplantation development of bovine embryos

Thioredoxin (TRX) is an ubiquitous protein disulfide reductase, which is known to be involved in the implantation development of mouse embryos. In the present study, recombinant human TRX was used to evaluate its effect on the promotion of preimplantation development of bovine embryos derived from in vitro maturation and fertilization. Supplementation of the medium 24h post insemination with TRX significantly (P<0.05) enhanced the frequency of development to the blastocyst stage in 5% O(2) concentration. The optimal concentration was 0.5 microg/ml (P<0.05, compared with 0, 0.1 and 1.0 microg/ml). This effect of TRX was evident only when added around the time of the first cleavage stage (24 h post insemination); no promotion was found with treatment at 6h (one-cell) or 44 h (six- to eight-cell) after insemination. Moreover, it is of interest that even with the best combination of the dose and timing of TRX treatment (0.5 microg/ml, at 24 h post insemination), no promotion of development was observed when embryos were cultured under 20% O(2). However, a preincubation of TRX in the culture medium under 20% oxygen for 24h did not diminish the promoting effect in the subsequent TRX treatment under optimal conditions, thus suggesting that the possible oxidation of TRX alone may not be the reason for the disappearance of the effect under a high oxygen concentration. These results indicate that TRX does improve the development of bovine embryos in vitro, though unlike the general reducing reagents such as beta-mercaptoethanol or cysteamine, TRX may have to exert its effect at specific times and in more physiologic oxygen environments.     

Parathyroid hormone receptor internalization is independent of protein kinase A and phospholipase C activation

Parathyroid hormone (PTH) and PTH-related peptide (PTHrP) binding to their common receptor stimulates second messenger accumulation, receptor phosphorylation, and internalization. LLC-PK(1) cells expressing a green fluorescent protein-tagged PTH/PTHrP receptor show time- and dose-dependent receptor internalization. The internalized receptors colocalize with clathrin-coated pits. Internalization is stimulated by PTH analogs that bind to and activate the PTH/PTHrP receptor. Cell lines expressing a mutant protein kinase A regulatory subunit that is resistant to cAMP and/or a mutant receptor (DSEL mutant) that does not activate phospholipase C internalize their receptors normally. In addition, internalization of the wild-type receptor and the DSEL mutant is stimulated by the PTH analog [Gly(1),Arg(19)]hPTH-(1-28), which does not stimulate phospholipase C. Forskolin, IBMX, and the active phorbol ester, phorbol-12-myristate-13-acetate, did not promote receptor internalization or increase PTH-induced internalization. These data indicate that ligand-induced internalization of the PTH/PTHrP receptor requires both ligand binding and receptor activation but does not involve stimulation of adenylate cyclase/protein kinase A or phospholipase C/protein kinase C.     

Participation of the rat caudate nucleus in the immunostimulating effect of DAGO

The data obtained suggest that administration of the DAGO increased the number of plaque- and rosette-forming cells after immunisation with the sheep red blood cells in the sham-operated Wistar rats. Following destruction of the caudate nucleus, the DAGO administration prevented the immune activation. Bilateral destruction of the caudate nucleus resulted in a considerable inhibition of the immune response as compared with the control rats. Thereupon the caudate nucleus seems to be involved in realisation of the DAGO-induced immune activation.