RESUMO
On inoculation of Nicotiana benthamiana with Bamboo mosaic virus (BaMV), a gene with downregulated expression was found involved in the infection cycle of BaMV. To uncover how this downregulated gene affects the accumulation of BaMV in plants, we used loss- and gain-of-function experiments. Knockdown of this gene decreased the accumulation of BaMV coat protein to approximately 60% in both plants and protoplasts of N. benthamiana but had no effect on Potato virus X and Cucumber mosaic virus infection. The full-length gene was cloned and revealed as an N. benthamiana nuclear-encoded chloroplast carbonic anhydrase (CA) and so designated NbCA. As compared with the accumulation of BaMV RNAs in NbCA-knockdown protoplasts, both plus- and minus-strand RNAs were reduced. We further fused NbCA with Orange fluorescent protein to confirm its localization in chloroplasts on confocal microscopy. However, transiently expressed NbCA in chloroplasts did not considerably increase BaMV accumulation. The addition of exogenous CA may not have any additive effect on BaMV accumulation because of the natural abundance of CA in chloroplasts. In an in vitro replication assay, the addition of Escherichia coli-expressed NbCA enhanced exogenous template level (re-initiation and elongation) but not endogenous template level (only elongation). These results suggest that NbCA is possibly involved in re-initiation step of BaMV RNA replication. Further analysis indicated that proton concentration could influence the endogenous and exogenous template activities. Hence, our results implied that NbCA could be playing a role in harnessing proton concentration and favoring the replicase with the re-initiation template.
RESUMO
BACKGROUND: Use of proximal tibia as a donor site has been applied in jawbone reconstruction since the 1990s. Catone and colleagues described a U-shaped incision made on the iliotibial tract during tibial cancellous bone procurement for maxillofacial reconstruction in 1992. We used a curvilinear incision on the iliotibial tract in lateral approach in our tibial cancellous bone harvesting procedure. OBJECTIVES: The objectives of this retrospective study are to describe our modified lateral approach for procuring cancellous graft from the proximal tibia and to assess the bone volume, donor site morbidity, and associated complications. MATERIAL AND METHODS: Eighty consecutive jawbone reconstructions utilizing autogenous tibial cancellous bone grafts in 78 patients from March 1998 through March 2008 were reviewed. The patient group consisted of 45 males and 33 females, ages 18 to 76 (average age 36.1 ± 12.3). Minimal postoperative follow-up period was 3 months. Unlike the traditional U-shaped trapdoor incision on the iliotibial tract, our curvilinear incision was made almost parallel to the fibers of that tract. RESULT: Only mild complications were observed at donor sites, including temporary paresthesia, gait disturbance, and an unpleasant scar. The average procured graft volume was 17.8 mL. We also present the first case of reconstruction of mandibular continuity defects of up to 6 to 7 cm lengthwise by tibial cancellous bone grafting, which has not previously been reported in the English literature. CONCLUSION: The modified incision on the iliotibial tract allowed access to obtain an equally good bone volume from the lateral aspect of the proximal tibia, and it rendered wound closure much easier than the procuring techniques described in the earlier literature.
