Despite the non-coding nature of their small RNA genomes, the visible symptoms of viroid infection resemble those associated with many plant virus diseases. Recent evidence indicates that viroid-derived small RNAs acting through host RNA silencing pathways play a key role in viroid pathogenicity. Host responses to viroid infection are complex, involving signaling cascades containing host-encode...

Linear, potato spindle tuber viroid RNA has been used as a substrate for an RNA ligase purified from wheat germ. Linear viroid molecules are efficiently converted to circular molecules (circles) which are indistinguishable by electrophoretic mobility and two-dimensional oligonucleotide pattern from viroid circles extracted from infected plants. In light of recent evidence for multimeric viroid ...

BACKGROUND Viroids are circular, highly structured, non-protein-coding RNAs that, usurping cellular enzymes and escaping host defense mechanisms, are able to replicate and move through infected plants. Similarly to viruses, viroid infections are associated with the accumulation of viroid-derived 21-24 nt small RNAs (vd-sRNAs) with the typical features of the small interfering RNAs characteristi...

Professor Hume was right: rootstocks are critical and much is still to be learned. Rootstocks and scions are the foundation of many tree fruit industries of the world. Together, those components establish profitability, but it can be argued that the rootstock is the critical component; otherwise, scions would be grown on their own roots everywhere. There is no precedent for the failure of a cit...

Recent research suggests that systemic signalling and communication between roots and leaves plays an important role in plant defence against herbivores. In the present study, we show that the oviposition of the two-spotted spider mite Tetranychus urticae in the systemic leaves of citrus rootstock Citrus aurantium (sour orange) was reduced by 50% when a lower leaf was previously infested with c...

Cell-free synthesis of citrus exocortis viroid (CEV) in nuclei-rich preparations from infected Gynura aurantiaca was optimum at 18-24 degrees C. Incubation of reaction mixtures at higher temperatures (30-36 degrees C) resulted in an increase of CEV linear molecules and the recovery of incomplete or nicked newly synthesized RNA species. Although the Mg(2+) optimum (2.5-5 mM) for CEV synthesis wa...

Previous work on citrus trees has shown that an interstock, grafted between the rootstock and scion combination, not only can improve tree growth, longevity, fruit production, and quality, but also can increase salinity tolerance. This research was designed to evaluate flooding responses of2-year-old 'Verna' lemon trees [Citrus limon (L.) Burm.; VL] either grafted on 'Sour' orange (C. aurantium...