No abstract

Stimulated by energetic stress, AMP-activated protein kinase (AMPK) controls several cellular functions. It was discovered here that infection of Vero cells with avian reovirus (ARV) upregulated AMPK and mitogen-activated protein kinase (MAPK) p38 phosphorylation in a time-and dosedependent manner. Being an energy status sensor, AMPK is potentially an upstream regulator of MAPK p38. Treatment with 5-amino-4-imidazolecarboxamide ribose (AICAR), a well-known activator of AMPK, induced phosphorylation of MAPK p38. Unlike AICAR, wortmannin or rapamycin did not induce phosphorylation of MAPK p38, suggesting that mTOR inhibition is not a determining factor in MAPK p38 phosphorylation. Inhibition of AMPK by compound C antagonized the effect of AICAR on MAPK p38 in Vero cells. Specific inhibition of AMPK by small interfering RNA or compound C also suppressed ARV-induced phosphorylation of MAPK kinase (MKK) 3/6 and MAPK p38 in Vero and DF-1 cells, thereby providing a link between AMPK signalling and the MAPK p38 pathway. The mechanism of ARV-enhanced phosphorylation of MKK 3/6 and MAPK p38 in cells was not merely due to glucose deprivation, a probable activator of AMPK. In the current study, direct inhibition of MAPK p38 by SB202190 decreased the level of ARV-induced syncytium formation in Vero and DF-1 cells, and decreased the protein levels of ARV sA and sC and the progeny titre of ARV, suggesting that activation of MAPK p38 is beneficial for ARV replication. Taken together, these results suggested that AMPK could facilitate MKK 3/6 and MAPK p38 signalling that is beneficial for ARV replication. Although well studied in energy metabolism, this study provides evidence for the first time that AMPK plays a role in modulating ARV and host-cell interaction. INTRODUCTIONAvian reovirus (ARV), which belongs to the family Reovirdae, is an important pathogen in poultry. Sharing much similarity with mammalian reovirus (MRV), the virion particles of ARV possess two layers of capsid and ten genome segments of dsRNA. The genome segments are divided into three size classes, designated L (large), M (medium) and S (small), depending on their electrophoretic mobility, that encode at least eight structural and four non-structural proteins (Benavente & Martínez-Costas, 2007). ARVs differ from their mammalian counterparts by their ability to cause massive cell fusion through the protein p10 (Bodeló n et al., 2002; Liu et al., 2008). Protein sC, encoded by the third open reading frame of the S1 segment, is a cell attachment protein (Martínez-Costas et al., 1997) as well as an apoptosis inducer (Shih et al., 2004). The major inner caspid protein, sA, encoded by the S2 genome segment, possesses non-specific nucleotidyl phosphatase activity (Yin et al., 2002). This protein is also reported to inhibit activation of dsRNA-dependent protein kinase (PKR) by competing for dsRNA (Martínez-Costas et al., 2000; González-Ló pez et al., 2003).AMP-activated protein kinase (AMPK) is a heterotrimer serine/threonine kinase consisting of a catalytic subun...

BackgroundThe chromosome-specific probe is a fundamental tool of chromosome painting and has been commonly applied in mammalian species. The technology, however, has not been widely applied in plants due to a lack of methodologies for probe development. Identification and labeling of a large number of oligonucleotides (oligos) specific to a single chromosome offers us an opportunity to establish chromosome-specific probes in plants. However, never before has whole chromosome painting been performed in rice.ResultsWe developed a pooled chromosome 9-specific probe in rice, which contains 25,000 oligos based on the genome sequence of a japonica rice (Oryza sativa L., AA, 2n = 2× = 24). Chromosome 9 was easily identified in both japonica and indica rice using this chromosome 9-painting probe. The probe was also successfully used to identify and characterize chromosome 9 in additional lines of O. sativa, a translocation line, two new aneuploids associated with chromosome 9 and a wild rice (Oryza eichingeri A. Peter, CC, 2n = 2× = 24).ConclusionThe study reveals that a pool of oligos specific to a chromosome is a useful tool for chromosome painting in rice.Electronic supplementary materialThe online version of this article (10.1186/s12870-018-1325-2) contains supplementary material, which is available to authorized users.

The interplay between avian reovirus (ARV) replication and apoptosis and proteasome pathway was studied in cultured cells. It is shown that inhibition of the proteasome did not affect viral entry and host cell translation but had influence on ARV replication and ARV-induced apoptosis. Evidence is provided to demonstrate that ubiquitin-proteasome blocked ARV replication at an early step in viral life cycle. However, viral transcription and protein translation were also reduced markedly after addition of proteasome inhibitor MG132. Treatment of BHK-21 cells with the MG132 markedly decreased virus titer as well as prevented virus-induced apoptosis. The expression of ARV proteins sigmaC, sigmaA, and sigmaNS was also reduced markedly, suggesting that suppression of virus replication is due to down-regulation of these ARV proteins by ubiquitin-proteasome system. MG132 was also shown to suppress ARV sigmaC-induced phosphrylation of p53 on serine 46, caspase 3 activities, and DNA fragmentation leading to complete inhibition of ARV-induced apoptosis.

No abstract