A novel RAV transcription factor from pear interacts with viral RNA-silencing suppressors to inhibit viral infection.

In plants, RNA silencing constitutes a strong defense against viral infection, which viruses counteract with RNA-silencing suppressors (RSSs). Understanding the interactions between viral RSSs and host factors is crucial for elucidating the molecular arms race between viruses and host plants. We report that the helicase motif (Hel) of the replicase encoded by apple stem grooving virus (ASGV)-the main virus affecting pear trees in China-is an RSS that can inhibit both local and systemic RNA silencing, possibly by binding double-stranded (ds) siRNA. The transcription factor related to ABSCISIC ACID INSENSITIVE3/VIVIPAROUS1 from pear (PbRAV1) enters the cytoplasm and binds Hel through its C terminus, thereby attenuating its RSS activity by reducing its binding affinity to 21- and 24-nt ds siRNA, and suppressing ASGV infection. PbRAV1 can also target p24, an RSS encoded by grapevine leafroll-associated virus 2 (GLRaV-2), with similar negative effects on p24's suppressive function and inhibition of GLRaV-2 infection. Moreover, like the positive role of the PbRAV1 homolog from grapevine (VvRAV1) in p24's previously reported RSS activity, ASGV Hel can also hijack VvRAV1 and employ the protein to sequester 21-nt ds siRNA, thereby enhancing its own RSS activity and promoting ASGV infection. Furthermore, PbRAV1 neither interacts with CP, an RSS encoded by grapevine inner necrosis virus, nor has any obvious effect on CP's RSS activity. Our results identify an RSS encoded by ASGV and demonstrate that PbRAV1, representing a novel type of RAV transcription factor, plays a defensive role against viral infection by targeting viral RSSs.

MdERFs, two ethylene-response factors involved in apple fruit ripening.

Two MdERFs (ethylene-response factors) were isolated from ripening apple (Malusxdomestica Borkh. cv. Golden Delicious) fruit. The features of their conserved motifs indicated that MdERF1 and MdERF2 belong to group VII and group IX categories in Arabidopsis, respectively. MdERF1 was expressed predominantly in ripening fruit, although a small degree of expression was also observed in non-fruit tissues, whereas MdERF2 was expressed exclusively in ripening fruit. The increased expression in ripening fruit was repressed by treatment with 1-methylcyclopropene (1-MCP: a potent antagonist of ethylene receptors), indicating that transcription is regulated positively by the ethylene signalling system. Indeed, it was a tendency for cultivars with low ethylene production to show lower MdERFs expression than those with high ethylene production. On the basis of concomitant analyses of the expression of some genes related to ripening, the functions of MdERFs and the role of ethylene in the ripening process are discussed.

[Temporomandibular joint ankylosis caused by systemic (distal) infection: a case report and literature review].

There were many causes for temporomandibular joint (TMJ) ankylosis including infection, trauma, degenerative changes and space-occupying lesion. This article reported a case of bilateral TMJ ankylosis caused by systemic (distal) infection. A 35-year old female patient complained of difficulty of opening mouth for about 20 years. She developed abscess in several places all over the body including bilateral TMJ 20 years ago. CT indicated that the condylar process was fused with the temporal bone. The patient was treated with resection of bilateral condylar/coracoid process and total joint prosthesis replacement. The maximal incisal opening was 2.5 cm 3 months post operation. The patient obtained a satisfied function of eating and speaking.

S-RNases from self-incompatible and -compatible apple cultivars: purification, cloning, enzymic properties, and pollen tube growth inhibitory activity.

Four S-RNases (RNase associated with self-incompatibility) were purified from the styles of two apple cultivars (Malus domestica), a self-incompatible cv., Starking Delicious (SD), and a self-compatible cv., Megumi (MG). Each cultivar produced two S-RNases and their enzymatic properties such as specific activity, pH optimum, thermal stability, and molecular mass, were characterized. The four S-RNases inhibited the tube growth of apple pollen in an in vitro bioassay at 25 microg/ml (1.0 microM), but did not distinguish self from non-self pollen. The cDNAs of four S-RNases were cloned, and the nucleotide and deduced amino acid sequences were analyzed. The nucleotide sequence of SD-Se RNase was a new one and the other was identical to that of Sc-RNase of cv. Fuji. In MG one was identical to the sequence of SD-Sc RNase and the other to that of Sa-RNase of cv. Golden Delicious except for one base. From results of the isolation amounts and the Western blot analysis for stylar crude extracts the amount of S-RNases in MG was apparently less than that in SD.