Distinct Effects of p19 RNA Silencing Suppressor on Small RNA Mediated Pathways in Plants

RNA silencing is one of the main defense mechanisms employed by plants to fight viruses. In change, viruses have evolved silencing suppressor proteins to neutralize antiviral silencing. Since the endogenous and antiviral functions of RNA silencing pathway rely on common components, it was suggested that viral suppressors interfere with endogenous silencing pathway contributing to viral symptom development. In this work, we aimed to understand the effects of the tombusviral p19 suppressor on endogenous and antiviral silencing during genuine virus infection. We showed that ectopically expressed p19 sequesters endogenous small RNAs (sRNAs) in the absence, but not in the presence of virus infection. Our presented data question the generalized model in which the sequestration of endogenous sRNAs by the viral suppressor contributes to the viral symptom development. We further showed that p19 preferentially binds the perfectly paired ds-viral small interfering RNAs (vsiRNAs) but does not select based on their sequence or the type of the 5’ nucleotide. Finally, co-immunoprecipitation of sRNAs with AGO1 or AGO2 from virus-infected plants revealed that p19 specifically impairs vsiRNA loading into AGO1 but not AGO2. Our findings, coupled with the fact that p19-expressing wild type Cymbidium ringspot virus (CymRSV) overcomes the Nicotiana benthamiana silencing based defense killing the host, suggest that AGO1 is the main effector of antiviral silencing in this host-virus combination

Peroxisomal acyl-CoA-oxidase deficiency: two new cases

We report on two new patients with straight-chain acyl-coenzyme A oxidase deficiency. Early onset hypotonia, seizures and psychomotor delay were observed in both cases. Plasma very-long-chain fatty acids were abnormal in both patients, whereas the plasma levels of phytanic acid, pristanic acid, the bile acid intermediates DHCA and THCA, and erythrocyte plasmalogen levels were normal. Studies in fibroblasts from the two patients revealed a deficiency of one of the two peroxisomal acyl-CoA oxidases, that is, straight-chain acyl-CoA oxidase (ACOX1). Subsequent molecular analysis of ACOX1 showed a homozygous deletion, which removes a large part of intron 3 and exons 4-14 in the first patient. Mutation analysis in the second patient revealed compound heterozygosity for two mutations, including: (1) a c.692 G > T (p.G231V) mutation and (2) skipping of exon 13 (c.1729_1935del (p.G577_E645del