Effekten av bladsvampsjukdomar hos nyponrosor

Roses are not only popular ornamentals, but some of the wild species also supply us with food, cosmetics and even medicine. Wild roses of the section Caninae, commonly known as dogroses, are often used for their fruits but may also harbour resistance genes that can be used for breeding healthier ornamentals. However, due to the special so-called Canina-meiosis, inheritance is mainly matroclinal with a comparatively small paternal contribution.Therefore, it is important to know how resistance genes are transmitted to the progeny. Different foliar fungi damage roses, most important are blackspot (Marssonina rosae) and powdery mildew (Sphaerotheca pannosa). Furthermore, rust (Phragmidium spec.) is known to infect roses, and a leafspot-disease called Sphaceloma rosarum has recently become more serious. Two fields with dogroses, one with plants obtained by open pollination in wild populations, and one with plants obtained from intra- and interspecific crosses, were evaluated for blackspot, powdery mildew, rust and leafspots in the autumn of 2005. The data was statistically analysed with Systat 5.2. Additionally, microscopic investigations were conducted to gather more knowledge about the appearance of the diseases on the dogrose species. Interestingly, no symptoms of powdery mildew were found in either field, although the fungus infected wild roses of a different section in a field closeby. The investigated dogrose plants had previously been damaged by powdery mildew, suggesting that the presently achieved tolerance is due to plant age or exterior influences. Surprisingly few symptoms of blackspot were found and they differed considerably from those found on ornamental cultivars, indicating a lower susceptibility. Most important in 2005 was rust, followed by leafspot symptoms. The latter were found to be caused not only by Sphaceloma rosarum, but also by Septoria rosae, a fungus never before noticed at Balsgård. The two leafspot diseases produce similar-looking spots that may vary somewhat depending on the host species, and can be properly discriminated only in a microscope. The rose species vary in their disease susceptibility but there was no evidence of really high levels of resistance. Amount of disease symptoms was mainly matroclinally inherited, but a contribution of the pollen parent was also found. Plants with Rosa rubiginosa as seed parent appear to be the most promising candidates for plant breeding since they performed best for rust and leafspots, and might even be resistant to Septoria-leafspot.Rosor är inte bara omtyckta som prydnadsväxter, några av de vilda arterna förser oss även med mat, kosmetika och till och med medicin. Vildrosor av sektionen Caninae, allmänt kända som nyponrosor, används ofta för sina frukter, men kan också innehålla resistensgener som kan utnyttjas för att framställa friskare prydnadsrosor. På grund av den särskilda så kallade Canina-meiosen är nedärvningen huvudsakligen maternell med ett jämförelsevis litet bidrag från fadern. Därför är det viktigt att veta hur resistensgener förs vidare till avkommorna. Olika bladsvampar som skadar rosor förekommer, vanliga är svartfläcksjuka (Marssonina rosae) och mjöldagg (Sphaerotheca pannosa). Dessutom är rost (Phragmidium spec.) känd för att infektera rosor och en bladfläcksjukdom orsakad av Sphaceloma rosarum har blivit alltmer vanligt förekommande. Två fält med rosor, varav ett med plantor som härstammar från fri avblomning, och ett med plantor från mellan- och inomartskorsningar, utvärderades för svartfläcksjuka, mjöldagg, rost och bladfläckar under hösten 2005. Erhållna data analyserades med Systat 5.2. Dessutom undersöktes symptomen i mikroskop för att öka kunskapen om sjukdomarnas utseende på nyponrosarter. Intressant var att inga symptom av mjöldagg hittades på något av fälten, trots att svampen infekterade vildrosor av en annan sektion på ett fält i närheten. De undersökta nyponplantorna hade angripits av mjöldagg tidigare år, därför ligger det nära till hands att tro att den förvärvade toleransen beror på plantornas ålder eller på yttre påverkan. Överraskande få symptom av svartfläcksjuka hittades och dessa var påfallande olika de symptom som hittades på prydnadsrossorter, vilket pekar på mindre mottaglighet hos nyponrosorna. Störst skada 2005 orsakades av rost, därefter följde bladfläckssymptom. De sistnämnda visade sig vara orsakade inte bara av Sphaceloma rosarum, utan också av Septoria rosae, en svamp som inte tidigare observerats på Balsgård. De två bladfläcksjukdomarna framkallar liknande fläckar som kan variera beroende på typ av värdväxt, och kan bara skiljas ordentligt under mikroskop. Rosarterna varierade i sin sjukdomsmottaglighet, men det fanns inga indikationer på verkligt höga nivåer av resistens. Graden av sjukdomssymptom visade huvudsakligen matroklin nedärvning, men bidrag från pollenföräldern hittades också. Plantor med Rosa rubiginosa som fröförälder tycks vara de mest lovande för växtförädling eftersom de var minst mottagliga för rost och bladfläckar och kanske även är resistenta mot Septoriabladfläckar

Biochemical and genetic analysis of RNA cap guanine-N2 methyltransferases from Giardia lamblia and Schizosaccharomyces pombe

RNA cap guanine-N2 methyltransferases such as Schizosaccharomyces pombe Tgs1 and Giardia lamblia Tgs2 catalyze methylation of the exocyclic N2 amine of 7-methylguanosine. Here we performed a mutational analysis of Giardia Tgs2, entailing an alanine scan of 17 residues within the minimal active domain. Alanine substitutions at Phe18, Thr40, Asp76, Asn103 and Asp140 reduced methyltransferase specific activity to <3% of wild-type Tgs2, thereby defining these residues as essential. Alanines at Pro142, Tyr148 and Pro185 reduced activity to 7–12% of wild-type. Structure–activity relationships at Phe18, Thr40, Asp76, Asn103, Asp140 and Tyr148, and at three other essential residues defined previously (Asp68, Glu91 and Trp143) were gleaned by testing the effects of 18 conservative substitutions. Our results engender a provisional map of the Tgs2 active site, which we discuss in light of crystal structures of related methyltransferases. A genetic analysis of S. pombe Tgs1 showed that it is nonessential. An S. pombe tgs1Δ strain grows normally, notwithstanding the absence of 2,2,7-trimethylguanosine caps on its U1, U2, U4 and U5 snRNAs. However, we find that S. pombe requires cap guanine-N7 methylation catalyzed by the enzyme Pcm1. Deletion of the pcm1(+) gene was lethal, as were missense mutations in the Pcm1 active site. Thus, whereas m(7)G caps are essential in both S. pombe and S. cerevisiae, m(2,2,7)G caps are not

Comparative Structural Analysis of Human DEAD-Box RNA Helicases

DEAD-box RNA helicases play various, often critical, roles in all processes where RNAs are involved. Members of this family of proteins are linked to human disease, including cancer and viral infections. DEAD-box proteins contain two conserved domains that both contribute to RNA and ATP binding. Despite recent advances the molecular details of how these enzymes convert chemical energy into RNA remodeling is unknown. We present crystal structures of the isolated DEAD-domains of human DDX2A/eIF4A1, DDX2B/eIF4A2, DDX5, DDX10/DBP4, DDX18/myc-regulated DEAD-box protein, DDX20, DDX47, DDX52/ROK1, and DDX53/CAGE, and of the helicase domains of DDX25 and DDX41. Together with prior knowledge this enables a family-wide comparative structural analysis. We propose a general mechanism for opening of the RNA binding site. This analysis also provides insights into the diversity of DExD/H- proteins, with implications for understanding the functions of individual family members

Separable Functions of the Fission Yeast Spt5 Carboxyl-Terminal Domain (CTD) in Capping Enzyme Binding and Transcription Elongation Overlap with Those of the RNA Polymerase II CTD ▿

An interaction network connecting mRNA capping enzymes, the RNA polymerase II (Pol II) carboxyl-terminal domain (CTD), elongation factor Spt5, and the Cdk7 and Cdk9 protein kinases is thought to comprise a transcription elongation checkpoint. A crux of this network is Spt5, which regulates early transcription elongation and has an imputed role in pre-mRNA processing via its physical association with capping enzymes. Schizosaccharomyces pombe Spt5 has a distinctive CTD composed of tandem nonapeptide repeats of the consensus sequence 1TPAWNSGSK9. The Spt5 CTD binds the capping enzymes and is a substrate for threonine phosphorylation by the Cdk9 kinase. Here we report that deletion of the S. pombe Spt5 CTD results in slow growth and aberrant cell morphology. The severity of the spt5-ΔCTD phenotype is exacerbated by truncation of the Pol II CTD and ameliorated by overexpression of the capping enzymes RNA triphosphatase and RNA guanylyltransferase. These results suggest that the Spt5 and Pol II CTDs play functionally overlapping roles in capping enzyme recruitment. We probed structure-activity relations of the Spt5 CTD by alanine scanning of the consensus nonapeptide. The T1A change abolished CTD phosphorylation by Cdk9 but did not affect CTD binding to the capping enzymes. The T1A and P2A mutations elicited cold-sensitive (cs) and temperature-sensitive (ts) growth defects and conferred sensitivity to growth inhibition by 6-azauracil that was exacerbated by partial truncations of the Pol II CTD. The T1A phenotypes were rescued by a phosphomimetic T1E change but not by capping enzyme overexpression. These results imply a positive role for Spt5 CTD phosphorylation in Pol Il transcription elongation in fission yeast, distinct from its capping enzyme interactions. Viability of yeast cells bearing both Spt5 CTD T1A and Pol II CTD S2A mutations heralds that the Cdk9 kinase has an essential target other than Spt5 and Pol II CTD-Ser2

Biochemical and genetic analysis of RNA cap

guanine-N2 methyltransferases from Giardia lamblia and Schizosaccharomyces pomb

Characterization of the Schizosaccharomyces pombe Spt5-Spt4 complex

The Spt5-Spt4 complex regulates early transcription elongation by RNA polymerase II and has an imputed role in pre-mRNA processing via its physical association with mRNA capping enzymes. Here we characterize the Schizosaccharomyces pombe core Spt5-Spt4 complex as a heterodimer and map a trypsin-resistant Spt4-binding domain within the Spt5 subunit. A genetic analysis of Spt4 in S. pombe revealed it to be inessential for growth at 25°C–30°C but critical at 37°C. These results echo the conditional spt4Δ growth phenotype in budding yeast, where we find that Saccharomyces cerevisiae and S. pombe Spt4 are functionally interchangeable. Complementation of S. cerevisiae spt4Δ and a two-hybrid assay for Spt4-Spt5 interaction provided a readout of the effects of 33 missense and truncation mutations on S. pombe Spt4 function in vivo, which were interpreted in light of the recent crystal structure of S. cerevisiae Spt4 fused to a fragment of Spt5. Our results highlight the importance of the Spt4 Zn2+-binding residues—Cys12, Cys15, Cys29, and Asp32—and of Ser57, a conserved constituent of the Spt4-Spt5 interface. The 990-amino acid S. pombe Spt5 protein has an exceptionally regular carboxyl-terminal domain (CTD) composed of 18 nonapeptide repeats. We find that as few as three nonamer repeats sufficed for S. pombe growth, but only when Spt4 was present. Synthetic lethality of the spt51-835 spt4Δ double mutant at 34°C suggests that interaction of Spt4 with the central domain of Spt5 overlaps functionally with the Spt5 CTD