We study the annulus amplitudes of (p, q) minimal string theory. Focusing on the ZZ-FZZT annulus amplitude as a target-space probe of the ZZ brane, we use it to confirm that the ZZ branes are localized in the strong-coupling region. Along the way we learn that the ZZ-FZZT open strings are fermions, even though our theory is bosonic! We also provide a geometrical interpretation of the annulus amplitudes in terms of the Riemann surface M p,q that emerges from the FZZT branes. The ZZ-FZZT annulus amplitude measures the deformation of M p,q due to the presence of background ZZ branes; each kind of ZZ-brane deforms only one A-period of the surface. Finally, we use the annulus amplitudes to argue that the ZZ branes can be regarded as "wrong-branch" tachyons which violate the bound α < Q/2.

The actin cytoskeleton has been implicated in the intra-and intercellular movement of a growing number of plant and animal viruses. However, the range of viruses influenced by actin for movement and the mechanism of this transport are poorly understood. Here we determine the importance of microfilaments and myosins for the sustained intercellular movement of a group of RNA-based plant viruses. We demonstrate that the intercellular movement of viruses from different genera [tobacco mosaic virus (TMV), potato virus X (PVX), tomato bushy stunt virus (TBSV)], is inhibited by disruption of microfilaments. Surprisingly, turnip vein-clearing virus (TVCV), a virus from the same genus as TMV, did not require intact microfilaments for normal spread. To investigate the molecular basis for this difference we compared the subcellular location of GFP fusions to the 126-kDa protein and the homologous 125-kDa protein from TMV and TVCV, respectively. The 126-kDa protein formed numerous large cytoplasmic inclusions associated with microfilaments, whereas the 125-kDa protein formed few small possible inclusions, none associated with microfilaments. The dependence of TMV, PVX, and TBSV on intact microfilaments for intercellular movement led us to investigate the role of myosin motors in this process. Virus-induced gene silencing of the Nicotiana benthamiana myosin XI-2 gene, but not three other myosins, inhibited only TMV movement. These results indicate that RNA viruses have evolved differently in their requirements for microfilaments and the associated myosin motors, in a manner not correlated with predicted phylogeny.cytoskeleton ͉ microfilaments ͉ tobacco mosaic virus ͉ potato virus X ͉ tomato bushy stunt virus

The p19 protein (P19) of Tomato bushy stunt virus (TBSV) is a pathogenicity determinant with host-dependent effects on virus spread and symptom induction. In addition, results in this study confirm that Potato virus X-mediated delivery of P19 suppresses posttranscriptional gene silencing (PTGS). To study the relevance of this activity for TBSV biology, we evaluated whether TBSV activates virus-induced gene silencing (VIGS) and if this process is suppressed by P19. TBSV vectors with the green fluorescent protein (GFP) gene, either active or inactive for P19 expression, were inoculated onto GFP-transgenic Nicotiana benthamiana plants. In the absence of P19 expression, VIGS was activated, as evidenced by the disappearance of GFP mRNA and green fluorescence. Coexpression of GFP and P19 from the TBSV vector suppressed VIGS, except in the newly emerging leaves. The suppressor activity required a central P19 region that is also known to be essential for host-dependent virus spread and symptom induction. Defective interfering RNAs (DIs) that contained the 3' end of the GFP gene induced silencing very effectively. The concomitant DI-instigated reduction in P19 accumulation failed to suppress this process, analogous to the known P19 dosage effects for other biological activities. In conclusion, (i) TBSV and its DIs are very effective inducers of VIGS, (ii) P19 is a strong suppressor of PTGS, (iii) P19 is a moderate suppressor of VIGS, and (iv) the suppressor activity is influenced by genetic and dosage features that are also important for P19-associated pathogenesis.

We examine the effect of the introduction of index futures trading in the Korean markets on spot price volatility and market efficiency of the underlying KOSPI 200 stocks, relative to the carefully matched non-KOSPI 200 stocks. Employing both an event study approach and a matching-sample approach for the market data during the period of January 1990-December 1998, we find that the introduction of KOSPI 200 index futures trading is associated with greater market efficiency but, at the same time, greater spot price volatility in the underlying stock market. We also find that KOSPI 200 stocks experience lower spot price volatility and higher trading efficiency than non-KOSPI 200 stocks after the introduction of futures trading. The trading efficiency gap between the two groups of stocks, however, declines over time and vanishes following the addition of options trading. Overall, our results suggest that while futures trading in Korea increases spot price volatility and market efficiency, there exists volatility spillover to stocks against which futures are not traded. We provide several factors unique in the Korean markets including circuit breakers, sidercar system, restrictions on foreign ownership, and inactive program trading as potential factors to explain some of our puzzling evidence. We further consider the potential effect of changes in daily price limits utilized by the Korea Stock Exchange during the testing period on our empirical findings.